Hey everyone,
I just wanted to see if anyone here would mind reading over the beginning three pages of a module which I have started writing, and let me know how it sounds. It is a horror based campaign, with inspirations from H.P Lovecraft. It will be focused on investigation and puzzles with an emphasis on picking ones fights wisely. I am intending for it to be taking place in the hive Tenebra, where a terrible accident took place involving a psyker/sorceror cult which displaced the hive city from reality and into a warp infested version of reality . I want to incorporate three separate levels of corruption. The first will be essentially normal, the vast majority of the citizens are living quite happily however they are timeless and immortal. The second has some minor corruption and the warp is quite present all around, and the third will be an absolute horror where only the most evil and brutally corrupted things live. I am intending to have the Pcs forced to navigate between the levels of reality, (though I am not sure what mechanic I am going to use for that), in order to escape and prevent the ultimate destruction of Scintilla.

Thanks regardless, constructive criticism is welcome and appreciated.

Anyways here it is:

Start:

(Isaac Maisinkov, 6 ft 2 brown thinning hair, large amount of scars and he carries a notched power sword on his back which no longer functions)

Begins on a massive carrier ship, Inquisitor Isaac Maisinkov has summoned the acolytes for their first mission.

Introductions blah de blah de blah (as they are customized to player's attitudes and responses)

Your first mission is to investigate possible missing ships around Lachesis, Scintillas' moon. I suspect that the reports are just the cause of common piracy and thus feel that I can entrust it to you, the newly enlisted. Your mission, investigate and eliminate the threats. I will provide you with a pilot, and a scout ship.

For the God Emperor!

(Gestures for acolytes to follow.)

Leads them to ship and then leaves.

Female pilot Quintilla Venria comes up, you can see that she is a veteran just by the amount of scars she has covering all her visible skin. She grimaces after the style of a grin and asks reduntantly "coming?" whilst boarding the ship.

The ship is cramped, without many amenities but thus is life. After a short while the ship takes off and begins the 3 day trek to Scintilla.

Shortly the acolytes can see the massive hive world growing bigger in the windows/view screens. The ship begins to turn a bit as it skives past Scintilla towards the moon Lachesis. A few minutes pass, when suddenly a shuddering is felt throughout the ship, it slowly intensifies until it is impossible to not fall over. Amongst the shuddering, one can hear the ship groaning and creaking as it begins to break up. The pressure of the ship suddenly disappears and everyone makes Toughness to prevent themselves from passing out. On failure they go unconcious, on success they stay awake one round, and must make a new Toughness test at the beginning of each round. Those who stay awake see the ship buckling and breaking around them, surrounded by a greenish, purple aura.

Everyone loses 1 fate point.

Everyone awakens at about the same time in pitch blackness. Eerily there is no sound. The air is hot, humid and a stench of sulphur taints it. Suddenly a great wrenching shock rocks the ground, and a distant boom signals the cause. The shock causes some of the debris overhead to fall, and the acolytes are bathed in a reddish light coming from the night sky. They can see that they are inside of a building of sorts, a ship sized hole has been punched through the upper layers. The night sky is like nothing anyone has ever seen before and upon looking at it, must roll -10 Willpower or roll on the shock table after which they gain d5 insanity. The stars seem to roil as if they were in a constant state of flux; the light they give off is a deep bloody red, and it feels completely wrong. (The light on ones skin causes a feeling like bugs crawling over it, and it shortly causes a headache. Psynicience to detect the warp tainting the light.)

Looking around the acolytes see that they are inside the now destroyed ship which they were travelling in. The ships hull has been rent in in-numerous locations, and it has an odd bend to it. It looks like a giant grabbed it and bent it with his hands while someone took an infinitely sharp razor and carved at the hull. It appears to have been painted red with blood. It is deemed irreparable by anyone with any tech-use. The pilot is not present and the on-board servitors appear to be completely dead as their head casings are cracked open and brain matter is oozing out. All valuable tools and devices on-board have been destroyed and are beyond salvaging.

Outside the ship is a nightmarish scene, the buildings around are cracked and decaying. Where the light shines on them seems to ooze blood but upon closer inspection there is none. The walls and ground seem to crawl a little bit as if they were alive, however they stop when someone is standing on, or touching them. There is vegetation is growing all around, a smell (It is the smell that everyone individually hates the most) comes off them, and they look as though they are on the verge of death.

A great many buildings are collapsed, however there are three which still have more or less open doorways: one is to the north, one to the northwest and one to the south east.

The door to the north opens into a small building which has mostly collapsed allowing the ghastly red light to make it appear bathed in blood. There are almost no practical things in here but there are quite a few pieces of memorabilia. Photos of a happy family with two kids, one boy one girl. When looked at the faces twist and mutate until they look monstrous even though one can tell who they used to be still. Upon twisting they move up to the front of the picture and the picture bends as though they are trying to get out, after a few seconds an angry scream issues forth. Willpower to avoid shock table. Other things include a stuffed animal with bleeding stabs. Ripped clothing.

The door to the northwest looks odd and opens into a house which feels odd. Light is limited. Perception to notice the entire house is seated with irregular angles. The door is canted 18 degrees to the left and the living quarters are canted 24 degrees to the right. There is a staircase to nowhere, indeed the door it leads to does not open and there is nought but solid wall behind it. On top of it all after a short amount of time within the house the feeling of being watched starts bothering the party. But the feeling is not a normal being watched, it feels like the gaze is one of unimaginable malignancy and anger watching them. Found amongst the wreckage of the house, is a poor quality bolt pistol with 2 shots in it.

Within the house to the south-east is nothing, but pitch blackness. Indeed it is so complete that light sources do not light even a meter in front of the bearer. Upon walking further in, the light becomes more dim but heavy breathing begins to emanate from the far side of the house. Walking towards it causes it to increase in speed, until it is fevered. After a small amount of time a beast rushes towards the party and it is initiative. This battle is fought in the dark and therefore the party suffers -20 to hit. (unless they increase the light by leaving.) The beast is very humanoid and yet looking into its warp twisted eyes makes it very clear that it is not. Its’ skin is sloughing off revealing greenish black muscle and thus causes a fear test. Upon being struck by this being one must make agility or suffer d5 corruption as its fluids sink in any exposed skin, burning through armor and clothing. Upon dying the beast melts into a puddle of black ichor which, gives off a smell much like the vegetation outside does.

After about 2 hours of in-game time, players start to feel itchy and painful even under what they are wearing, and nothing helps. Every minute after and every minute after that, everyone suffers a level of fatigue. Once everyone passes out roll d5+7 corruption.

minor quibbles here and there - more stylistically than anything else, then I got to:

"Everyone loses a fate point"

And I thought to myself "WTF?!"

Aside from not specifying if this is temporary of permanent Fate (that is, "spend" vs "burned"), I know that sort of high-handed thing would cause resentment from some if not all of my players. Especially in what's largely the sell text. They haven't had a chance by then to do anything, nor make any decission as far as I can tell from your writings.

And that's ... not good design, at least in the design philosophy I usually follow.

Can't really comment on anything after that - was too annoyed to even read it.

Sorry.

minor quibbles here and there - more stylistically than anything else, then I got to:

"Everyone loses a fate point"

And I thought to myself "WTF?!"

Aside from not specifying if this is temporary of permanent Fate (that is, "spend" vs "burned"), I know that sort of high-handed thing would cause resentment from some if not all of my players. Especially in what's largely the sell text. They haven't had a chance by then to do anything, nor make any decission as far as I can tell from your writings.

And that's ... not good design, at least in the design philosophy I usually follow.

Can't really comment on anything after that - was too annoyed to even read it.

Sorry.

Fair enough,

I wanted to emphasize that they are saved by the God Emperor in order to fulfill the greater mission, which they are entering into.

Do you have any ideas about how I could emphasize that without being overly cliche'?

Not trying to be snarky or anything.

I am a new gm writing a homebrew for the first time, so any help is appreciated.

(the style issues are just a result of me not fine tuning it as I have only just started writing it, I will improve the dialogue and whatnot later, but again any suggestions on improvements are welcome)

Do you have any ideas about how I could emphasize that without being overly cliche'?

Yes! Embrace the cliché, love it, own it and use the hell out of it. They are what they are for a reason: they work. Perhaps most of all in RPGs.

So throw in the ghost of Saint Drusus, and dial it to 11. Don't ever be afraid to ram it home that they're on a mission for the God-Emperor.

But don't do the FP loss. Fate Points are partly a last resort (which you always want them to have because it's very easy to destroy them, and for them to destroy themselves), and also their only authorial tool (their way to take narrative control). You'll find the game runs better when your players have a few of them, and when players can rely on them as a strictly meta resource that you never screw with.

...

The vegetation with individualised stench is a nice touch, but it's the sort of thing you shouldn't just hand to players. Save it for if/when they make a roll to investigate their environment. Things like this are much more effective used like that.

...

If you're going to Warp Shock your players, make sure to foreshadow it properly and give them a chance to get the hell out of there first.

From a player perspective, doing otherwise comes across as you being unfair.

From a campaign perspective, if this is much more than a one-off, you need to be very careful with Insanity & Corruption Points, because they're an inevitable doom and they can be a very quick one if you're not careful how you dish them out.

...

Combat encounters need more fleshing out. You need to to figure out what exactly the environment is, and where everything is located. And include at least 5 things that can impact the fight. Right now you have lighting conditions. That's good, but you need another 4.

- Fine, you don't necessarily need 5 things, but it is a very good rule of thumb. Think verticality, utilities, vulnerabilities and cover, cover, cover.

...

You're not writing a play or a novel, so unless you plan on actually rehearsing everything you've written down for a wordperfect recital at the table, your method of writing is terrifyingly inefficient.

Use keywords and short sentences.

FX: Blood-like lighting, twisting images, spooky ****.

Then riff off of that in actual play. It'll make the game flow far more naturally than if you read out 10+ lines to your players.

Especially because you are - I guarantee - going to go off script at times, and make stuff up you hadn't planned for, which you'll then have to edit-on-the-fly into the blurbs you read aloud for your players. That's really, really not a good way to handle things.

Also: don't bury things like rolls into descriptive text, or you'll miss it when you get to the table, or worse, remember but need time to find the details. It's disruptive and annoying to everyone.

...

All that said, I love where you're going with this

Do you have any ideas about how I could emphasize that without being overly cliche'?

Yes! Embrace the cliché, love it, own it and use the hell out of it. They are what they are for a reason: they work. Perhaps most of all in RPGs.

So throw in the ghost of Saint Drusus, and dial it to 11. Don't ever be afraid to ram it home that they're on a mission for the God-Emperor.

But don't do the FP loss. Fate Points are partly a last resort (which you always want them to have because it's very easy to destroy them, and for them to destroy themselves), and also their only authorial tool (their way to take narrative control). You'll find the game runs better when your players have a few of them, and when players can rely on them as a strictly meta resource that you never screw with.

...

The vegetation with individualised stench is a nice touch, but it's the sort of thing you shouldn't just hand to players. Save it for if/when they make a roll to investigate their environment. Things like this are much more effective used like that.

...

If you're going to Warp Shock your players, make sure to foreshadow it properly and give them a chance to get the hell out of there first.

From a player perspective, doing otherwise comes across as you being unfair.

From a campaign perspective, if this is much more than a one-off, you need to be very careful with Insanity & Corruption Points, because they're an inevitable doom and they can be a very quick one if you're not careful how you dish them out.

...

Combat encounters need more fleshing out. You need to to figure out what exactly the environment is, and where everything is located. And include at least 5 things that can impact the fight. Right now you have lighting conditions. That's good, but you need another 4.

- Fine, you don't necessarily need 5 things, but it is a very good rule of thumb. Think verticality, utilities, vulnerabilities and cover, cover, cover.

...

You're not writing a play or a novel, so unless you plan on actually rehearsing everything you've written down for a wordperfect recital at the table, your method of writing is terrifyingly inefficient.

Use keywords and short sentences.

FX: Blood-like lighting, twisting images, spooky ****.

Then riff off of that in actual play. It'll make the game flow far more naturally than if you read out 10+ lines to your players.

Especially because you are - I guarantee - going to go off script at times, and make stuff up you hadn't planned for, which you'll then have to edit-on-the-fly into the blurbs you read aloud for your players. That's really, really not a good way to handle things.

Also: don't bury things like rolls into descriptive text, or you'll miss it when you get to the table, or worse, remember but need time to find the details. It's disruptive and annoying to everyone.

...

All that said, I love where you're going with this

Wow....

thanks for this

I appreciate all the info, I was coming at writing the module in the wrong way. I was trying to write it like a fully fledged play/story but what you said makes a lot of sense. I really appreciate the optimism and the positive tone you used in telling me the info, and will be sure to use a great deal of it. This is exactly what I was asking for as again I am new to home-brewing games, and was not expecting the hostility of being told that my first idea was crap and thus the rest weren't worth reading without any real explanation.

One question if you would be so kind, in terms of the ideas I wrote for the hook of the campaign and the stage setting, how are they? just from your perspective.

Thanks again

I was trying to write it like a fully fledged play/story but what you said makes a lot of sense.

Commercial modules are written the way they are, because they don't have the advantage of being written by the people who're supposed to run them.

You do have the advantage of writing for yourself, so you automatically have the feel for the module. You don't need a long and flowery description of a scene, just a couple of keywords to help you remember what you imagined it to be.

This is actually very, very important and with the exception of combat, applies to All Things Prep. Because otherwise you're going to drown yourself in work and slow yourself down at the table. And just to add frustration on top, most of your work you'll never actually use.

This is exactly what I was asking for as again I am new to home-brewing games, and was not expecting the hostility of being told that my first idea was crap and thus the rest weren't worth reading without any real explanation.

To be a little bit fair, messing with Fate Points is probably the biggest No-No in a Dark Heresy game. They really, really need to be something that only your players control.

Along similar lines, be very, very careful about attaching negative consequences to successful rolls. This can work. But it's the sort of stunt you do not pull unless you have a fantastic narrative reason, and you are 110% certain your players won't end up feeling like you're arbitrarily punishing them.

One question if you would be so kind, in terms of the ideas I wrote for the hook of the campaign and the stage setting, how are they?

I love the overall concept.

I'm afraid I'm drawing a blank when it comes to concrete suggestions on how, but it would probably be a good idea to foreshadow the current state of Hive Tenebra. If you're running a game now, maybe you could work in an urban legend hinting at its fate or something?

The Shripwrecked Into Madness is brilliant. Like I said above, don't be afraid to really play up the divine intervention. The idea that the longer-conscious Acolytes could have clearer and clearer visions of, for example, Saint Drusus, carrying them to safety springs readily to mind and would please the hell out of me if I was one of your players

Generally speaking when designing modules, it's a good idea to start with the end. Though normally this applies to plot, not environment. I bring it up mostly because I'm not clear on what you intend with the three stages of Wrap'edness of Tenebra you mentioned in the OP. You may want to start by defining the extreme and work your way backwards.

In case you were unaware or hadn't considered it, working the plot backwards is one of better and definitely one of the easier ways to go about it. Start with what would happen if the Acolytes were never there, then work backwards and throw in opportunities for the Acolytes to upset things.

Also, once you've got everything nailed down, it's a really good idea to create a flowchart of the scenes. It's an amazingly helpful reference to have at the table, especially when things go off track - and they will. Count on it. There's no such thing as predicting what a bunch of Acolytes are going to do

Good luck, and don't let one grumpy reply stop you from asking all you want. Being a good GM who has fun is in large part a skill, and as is mostly the case with skills, it's a lot easier to learn when you have people you can learn from

I was trying to write it like a fully fledged play/story but what you said makes a lot of sense.

Commercial modules are written the way they are, because they don't have the advantage of being written by the people who're supposed to run them.

You do have the advantage of writing for yourself, so you automatically have the feel for the module. You don't need a long and flowery description of a scene, just a couple of keywords to help you remember what you imagined it to be.

This is actually very, very important and with the exception of combat, applies to All Things Prep. Because otherwise you're going to drown yourself in work and slow yourself down at the table. And just to add frustration on top, most of your work you'll never actually use.

This is exactly what I was asking for as again I am new to home-brewing games, and was not expecting the hostility of being told that my first idea was crap and thus the rest weren't worth reading without any real explanation.

To be a little bit fair, messing with Fate Points is probably the biggest No-No in a Dark Heresy game. They really, really need to be something that only your players control.

Along similar lines, be very, very careful about attaching negative consequences to successful rolls. This can work. But it's the sort of stunt you do not pull unless you have a fantastic narrative reason, and you are 110% certain your players won't end up feeling like you're arbitrarily punishing them.

One question if you would be so kind, in terms of the ideas I wrote for the hook of the campaign and the stage setting, how are they?

I love the overall concept.

I'm afraid I'm drawing a blank when it comes to concrete suggestions on how, but it would probably be a good idea to foreshadow the current state of Hive Tenebra. If you're running a game now, maybe you could work in an urban legend hinting at its fate or something?

The Shripwrecked Into Madness is brilliant. Like I said above, don't be afraid to really play up the divine intervention. The idea that the longer-conscious Acolytes could have clearer and clearer visions of, for example, Saint Drusus, carrying them to safety springs readily to mind and would please the hell out of me if I was one of your players

Generally speaking when designing modules, it's a good idea to start with the end. Though normally this applies to plot, not environment. I bring it up mostly because I'm not clear on what you intend with the three stages of Wrap'edness of Tenebra you mentioned in the OP. You may want to start by defining the extreme and work your way backwards.

In case you were unaware or hadn't considered it, working the plot backwards is one of better and definitely one of the easier ways to go about it. Start with what would happen if the Acolytes were never there, then work backwards and throw in opportunities for the Acolytes to upset things.

Also, once you've got everything nailed down, it's a really good idea to create a flowchart of the scenes. It's an amazingly helpful reference to have at the table, especially when things go off track - and they will. Count on it. There's no such thing as predicting what a bunch of Acolytes are going to do

Good luck, and don't let one grumpy reply stop you from asking all you want. Being a good GM who has fun is in large part a skill, and as is mostly the case with skills, it's a lot easier to learn when you have people you can learn from

Well thanks again for the amazing response,

you certainly seem to know what you are talking about.

I have played a fair amount of dark heresy however I guess my gm is too nice, as I never found fate points to be as instrumental as has been stated. I apologize if it sounded like undue bitching about them.

The advice about beginning at the end and working my way back is great, however for this current module I have the premise but no ending or middle part. lol However I feel that once I really get into it, it will show itself, at least I hope so.... The idea of establishing the worst possible level as you put it is a great idea though, as then I will have a much easier time figuring out the other two based on it. I do intend to establish the fact of why/how hive Tenebra is what it is and is very much the reason for why I chose to base it in Tenebra in the first place. (unexplained phenomena, mixed with conspiracy theories = perfect location for a story, at least imo)

I appreciate the advice about not attaching negative things to successful player rolls, unless as you stated it is a very dramatic and narrative time. (I likely would have screwed up with that and caused contention between me and the players).

I will definitely create a flowchart, and was intending on creating a gm only map too, just for easier reference.

Thanks again for all the help, I feel much better and relaxed about creating this module, (with the idea of using notes instead of writing a full story) as it will likely be 30 pages instead of 300. lol

This is exactly what I was asking for as again I am new to home-brewing games, and was not expecting the hostility of being told that my first idea was crap and thus the rest weren't worth reading without any real explanation.

Yeah, sorry about that. I need to learn to stop going to forums when I should be in my bed. I can only offer my apologies for that.

OK; as a GM, about the most valuable thing you can offer to your players are choices. The more you dictate the story, the less involved they will feel. To engage them in the story, make the story depend on their own decissions.

This is also (part of) the reason why fate points are so valuable. They are the mechanic players have to affect the story and invoke cinematic luck (that is, luck just when they need it). Don't give them out willy-nilly, but don't arbitrarily take them away either.

This btw is also why I disagree with those GMs out there who deny their players some the uses of Fate Points. The setting it dark and gritty, but over the top and driven by the Rule of Cool. To achieve this mix you (as players) need cinematic luck, which is what Fate Points are there to provide. Too few and you go into overly grim-dark. Too many and you might as well be playing Exalted.

Otherwise Simsum has a lot of excellent advice - and is probably better at phrasing it than I ever could be.

So I'll try to throw in a few thoughts:

• Try to write open rather than closed stories. published scenarios are limited in that they cannot make many assumptions about the GM no the group. If you're just writing to your own group, take advantage of this! Use recurring NPCs! Re-use locations. Use the specialties of the characters, rather than having some NPC come in from the sideline with the skills to solve things. Focus the story on the PCs.
• Make the world around them feel real. Details are good. Sensory input makes the world seems like somethign that could really be there.
• Make the world around them consistent. Walking down the same road takes you to the same place every time - if it doesn't, there should be a reason for this. If you've established that something works the same way every time, you can make a plot hook out of that thing changing. "Why is that fellow wearing a red sleeve? No-one here wears red sleeves since the invasion 80 years ago! And even wierder, why isn't anyone commenting on it?!"
• NPCs that don't matter for the story itself can re-appear again and again. They can become a fixture and a story tool in and of themselves. When I ran a lot of shadowrun some years ago, I had this element called Jamie's All Night Guns and Liquor Stor. Always open, always on the same corner in Seattle. The owner and proprietor would have been a rip-off of Abu from the Simpsons if I'd actually seen an episode of the Simpsons back then.He was always there are helpful and had a bit of extra ammo when the PCs needed it. Then one day, he mentioned having noticed something odd. I was surprised to see how fast the players jumped at this - I had to re-plan the entire evening just because my planned foreshadowing was so much stronger than my actual planned hook.
• Pay attention to your players. What stories do they want? A lot of action? Deep emotional drama? Horror? Try to work out how this can be combined with the stories you want to tell.
• Surprises are the spice of life, To quote: "I have players so that they can come up with things I'd have never thought of. If I didn't want to be surprised, I'd be an author, not a GM."

This is exactly what I was asking for as again I am new to home-brewing games, and was not expecting the hostility of being told that my first idea was crap and thus the rest weren't worth reading without any real explanation.

Yeah, sorry about that. I need to learn to stop going to forums when I should be in my bed. I can only offer my apologies for that.

OK; as a GM, about the most valuable thing you can offer to your players are choices. The more you dictate the story, the less involved they will feel. To engage them in the story, make the story depend on their own decissions.

This is also (part of) the reason why fate points are so valuable. They are the mechanic players have to affect the story and invoke cinematic luck (that is, luck just when they need it). Don't give them out willy-nilly, but don't arbitrarily take them away either.

This btw is also why I disagree with those GMs out there who deny their players some the uses of Fate Points. The setting it dark and gritty, but over the top and driven by the Rule of Cool. To achieve this mix you (as players) need cinematic luck, which is what Fate Points are there to provide. Too few and you go into overly grim-dark. Too many and you might as well be playing Exalted.

Otherwise Simsum has a lot of excellent advice - and is probably better at phrasing it than I ever could be.

So I'll try to throw in a few thoughts:

• Try to write open rather than closed stories. published scenarios are limited in that they cannot make many assumptions about the GM no the group. If you're just writing to your own group, take advantage of this! Use recurring NPCs! Re-use locations. Use the specialties of the characters, rather than having some NPC come in from the sideline with the skills to solve things. Focus the story on the PCs.
• Make the world around them feel real. Details are good. Sensory input makes the world seems like somethign that could really be there.
• Make the world around them consistent. Walking down the same road takes you to the same place every time - if it doesn't, there should be a reason for this. If you've established that something works the same way every time, you can make a plot hook out of that thing changing. "Why is that fellow wearing a red sleeve? No-one here wears red sleeves since the invasion 80 years ago! And even wierder, why isn't anyone commenting on it?!"
• NPCs that don't matter for the story itself can re-appear again and again. They can become a fixture and a story tool in and of themselves. When I ran a lot of shadowrun some years ago, I had this element called Jamie's All Night Guns and Liquor Stor. Always open, always on the same corner in Seattle. The owner and proprietor would have been a rip-off of Abu from the Simpsons if I'd actually seen an episode of the Simpsons back then.He was always there are helpful and had a bit of extra ammo when the PCs needed it. Then one day, he mentioned having noticed something odd. I was surprised to see how fast the players jumped at this - I had to re-plan the entire evening just because my planned foreshadowing was so much stronger than my actual planned hook.
• Pay attention to your players. What stories do they want? A lot of action? Deep emotional drama? Horror? Try to work out how this can be combined with the stories you want to tell.
• Surprises are the spice of life, To quote: "I have players so that they can come up with things I'd have never thought of. If I didn't want to be surprised, I'd be an author, not a GM."

Firstly thanks for the apology, no worries.

I appreciate the explanation, and it is very good to know. I want to be a good GM not a sh*tty one so it was good to read that about fate points and choices. The advice you gave looks very sound and I will definitely learn from it. Any advice on how to make a setting realistic but fantastical at the same time? Should I just include a lot of description and keep it consistent?

Thanks for the help, and bothering to come back and look again.

Any advice on how to make a setting realistic but fantastical at the same time? Should I just include a lot of description and keep it consistent?

Thanks for the help, and bothering to come back and look again.

Ofcourse I'd come back with an apology, as soon as I'd slept and realised how rude I'd been

Learn to improvise. Players will go off your planned track once in a while - if you can make it feel just as real as when they are following your planned trail, even as you're maneuvering back on track, you'll be an awesome GM.

And luckily a good way to practice this (I think) is making up details.

The above mentioned "no-one here wears red sleaves after that invasion 80 years ago!" is an example. Or perhaps one of the characters is not-local, and think the way the locals depict some saint to be just wrong !

It's not really about giving a lot of description, it's more about being able to give the illusion of a complete world, without actually burdening people with too much info. And details about this thing or that helps that illusion.

Just piling on descriptions risks overloading your players - some more than others.

As an example, I love the books by JRR Tolkien, but one of my players complains extensively about how he will spend pages describing the characters' surroundings and what they see. So she needs less description - remember what I wrote about paying attention to your players above?

As for consistency, it really is that important I think. With rules, and with the world you describe.

If you make a ruling, make sure you keep to it, regardles of who it favours. On the other hand, don't be afraid to admit you were wrong. - but make sure you tell the players what you did wrong and how, so that they know what to expect.

Perhaps this is really what's at the heart of being consistent.

When I drop a ball, I expect it to fall to the ground, every time. If my character drops a ball, I expect it to drop to the ground every time, but I can't actually know, because there are no laws of physics, only the decissions of the GM. If the "rules of reality" change, players can't predict (or even guess at) the results of their actions, and this removes their motivation.

In my experience, actual rules matter a lot less than that these rules are consistent. But that might depend on the group.

If you can master these steps, it's unlikely that things will go catastrophically wrong for you

Late to the party, as ever, but here are my 2 (euro)cents.

In addition to agreeing with everything Simsum has said, I'll add some suggestions to your plot. This warp-cult wants to bring the entire sector into ruin and chaos by destroying its seat of power and those ruling it: Scintilla. The warped Tenebra is just the start, unless the Acolytes can stop this, the tear in the veil between realities will grow, and tear the entire planet in "two".

Perhaps not literally, as in blown into tiny pieces, but "two" as in existing in and out of the warp, with all the insanities and horrors that involves. Scintilla becomes a new "eye of terror" and the source of many a Black Crusade.

There's your ending, if the Acolytes fail.

Now work backwards from that. What will they need to do in order to stop this?

Find the cult, learn of the ritual, discover how to stop this? Perhaps they need some allies on the way. Time to make friends, earn trust, unite warring factions, etc. Many possibilities here.

Perhaps they need to recover some specific artefact? A macguffin that can heal the wounds in space and time. Think "quest for the holy grail", with challenges along the way.

Late to the party, as ever, but here are my 2 (euro)cents.

In addition to agreeing with everything Simsum has said, I'll add some suggestions to your plot. This warp-cult wants to bring the entire sector into ruin and chaos by destroying its seat of power and those ruling it: Scintilla. The warped Tenebra is just the start, unless the Acolytes can stop this, the tear in the veil between realities will grow, and tear the entire planet in "two".

Perhaps not literally, as in blown into tiny pieces, but "two" as in existing in and out of the warp, with all the insanities and horrors that involves. Scintilla becomes a new "eye of terror" and the source of many a Black Crusade.

There's your ending, if the Acolytes fail.

Now work backwards from that. What will they need to do in order to stop this?

Find the cult, learn of the ritual, discover how to stop this? Perhaps they need some allies on the way. Time to make friends, earn trust, unite warring factions, etc. Many possibilities here.

Perhaps they need to recover some specific artefact? A macguffin that can heal the wounds in space and time. Think "quest for the holy grail", with challenges along the way.

I like this

I hope you don't mind if I take it and change it around a bit

I was thinking of having friendly mutants (Think Fallout 3) as basically townsfolk for limited shopping purposes, and whatnot.

Thanks for the ideas they are definitely interesting

You do have the advantage of writing for yourself, so you automatically have the feel for the module. You don't need a long and flowery description of a scene, just a couple of keywords to help you remember what you imagined it to be.

That is sound advice, however I do not entirely agree. I for my share can best think while typing, so I tend to do exactly that: long, flowery descriptions, fleshed-out NPC dialogue. Most of the times, ideas only come to me while writing in full sentences. Granted, I don't use the stuff I write at the game table, for once I've written it down it is commited to memory, and I do make an effort to condense the walls of text into buzzwords to use in game. But in my experience, my players have so far enjoyed my sometimes long-winded descriptions of people and environments which I would not have been able to make up on the fly from a fey keywords. That is probably a rather unusual approach, and yes, it is a lot of work, but I never felt it to be wasted time to flesh out things beforehand...

But hey, that's just how I like to do it, not how anyone else has to do it. Just pointing out there's more than one approach, and you have to find the one that works for you and your group.

aaaalso, since Sim mentioned combat encounter accuracy, might I point you to this thread that has helped me enourmously:
http://community.fantasyflightgames.com/index.php?/topic/101369-wanted-advice-on-effective-combat/

Especially the bit about map design by Covered in Weasels, which I dare copypaste here:

I try to follow these guidelines when designing combat encounter maps:

1. Provide cover for both players and enemies. Ideally there will be multiple different strengths of cover -- for example, a chapel might have many ARM 8 wooden pews and several ARM 16 stone pillars in the main floor area. Interior walls of buildings are usually ARM 8 unless they are reinforced in some way; modern rifles can pierce a typical wall and hit somebody on the other side with enough force to cause injury.
2. Provide routes for combatants to flank or charge each other. A straight corridor shoot-out generally makes for poor tactical gameplay. Have stairs and balconies that pass above or below the main combat floor. Perhaps some routes are faster or safer than others but require a skill check to cross -- instead of walking around the edge of a pit full of hazardous waste, a character could use Acrobatics to cross the narrow girders leading across the pit.
3. Let players interact with the environment in some way. Maybe tables can be flipped to provide cover, or an industrial lift can be raised to give someone a height advantage. Players can shoot pipes to produce a cloud of steam, duplicating the effects of a smoke grenade. Entering the proper code into a computer terminal (Tech-Use) could reprogram nearby repair servitors to attack your enemies.
4. Give the players an objective besides "kill everyone." Maybe an important target is fleeing while minions and traps cover his retreat. Do the players advance cautiously and risk losing their quarry, or do they rush the enemy and possibly expose themselves to serious harm? Maybe the party Adept has to decrypt some vital data and must be protected while a large force of mercenaries tries to stop him, and the Acolytes must hold out against a superior enemy while the non-combat party member makes an extended skill test. If the Acolytes want to take a cult leader alive so they can interrogate him, they will hesitate to use their boltguns and power swords against a potentially dangerous enemy.

Uhm, sorry for multi-posting, I seem to be a bit disorganised -.-

What has not been pointed out so far is atmosphere. It's one of the many roles of the GM to create atmosphere that will immerse players and make them forget they are sitting round a table, and one that new GM in particular tend to overlook with their hands full. Since you use a setting that's supposed to be rather creepy, I'd wager that it'd pay off to put some thought into the matter.
So, my advice on creating atmosphere (mind you, this is all how I like it, not something I'd force on a group if they don't like that sort of thing):

- Descriptions: Don't tell your players there's "kinda a building", but "there's a dilapidated habblock, grey ferrocrete, in places plastered over with flaking paint that has yellowed. A lone lumenglobe spills dim light over the cracked stairs."
As has been pointed out before, this can be overdone, so don't drown your players in details, but whenever you want to shine a spotlight on specific ppl, events, environments, or envoke a particular emotion, this is the tool of choice.

- In Character: Whenever possible, use direct speech when portraying NPCs. That is, don't tell your players "the guy tells you that he has seen the person in question yesterday", but spell it out, adopt the NPC's manner of speech, choice of words, facial expressions, body language, slang, act as good as you can. Is she a noble with windy speech or an underhive scum? It also serves as giving away clues - if you're talking in-character and the character hesitates before answering, players will know that something's amiss (if they paid attention) without the need of a dice-roll.

Also, encourage your players to do the same. It's weird in the beginning, but it definitely pays off, immersion-wise.

- No Jokes. There's nothing wrong with good humour at the gaming table! Especially in the beginning phase, we do have a lot of laughs. But if you're trying to build atmosphere, there's nothing more immersion breaking than a joke at the wrong time. Even though it might be brilliant, when you're delivering an emotional scene, a flat joke will destroy everything you've worked for for a few seconds of laughter. Same goes for off-topic discussions, smoke breaks etc., cut those as short as possible, ask your players to focus on the game. That's not being a draconian, humourless overlord, but simply politely getting things on track. Sacrificing a few bits of socializing and laughter every other weekend will gain you something far more valuable: a memorable, immersive story you made yourself

- Exterior factors: if you can manage, try to shut out the outer world. No persons barging into the room turning on the TV, if at all possible, no kids running around crying for attention from mom (we had that once ~shudder~), or mom peeking curiously into the room to see what her kids are up to. Try to play in a secluded spot and at a time with smallest possible amounts of distractions.

I prefer a rather dim lighting while playing, further drenching the outer world in shadow, but that's personal taste. Also, I use a laptop with ready-made playlists for background music, generic sountrack collections (games are excellent) with tracks sorted into categories such as "heroic", "sad", "combat", "neutral background", "sacral" and so on. It's a bit of a workload to get your initial playlists, but you can use and extend them for years, and in my experience, music makes one hell of a difference concerning atmosphere.

We even have been using intro tracks for years (atm Spirits Within by Audiomachine), that we play after having summed up the last session and before starting to actually play. It works well as defining the transition from out-game to in-game, gives players the opportunity to focus on their character for a few minutes and the GM to have a last quick look over notes or get rid of all the reallife-ballast clogging up imagination.

I'm aware that this is quite a lot for starters, I'm not trying to intimidate you or enforce on you my Golden Standard, truly! These are just my experiences -pick what you like and what works for you, discard the rest

No worries, I want every little bit of advice I can get.
Thank you for taking the time to respond, and the points you made about immersion are especially good. I agree 100% that immersion is necessary to have a proper roleplaying session and that it will likely be much more satisfying for everyone involved if they actually get sucked into the story.

Just wanted to say as well that thus far I am very impressed with the people who frequent these forums as they have been very kind and intelligent in their posts.
Again, thank you all for helping me with my striking out as a new DM, and any more advice which anyone has to offer is very welcome.