Alright. So I should first claim that in the ways of the warhammer 40K universe I am NOT new. I know a lot of the lore: Both cannon and theory and just plain outright stupid.

I am also not new to being a Game master, I have run both Dungeons and Dragons and Heroes Unlimited.

My newness comes from the Dark Heresy part.

I found Edge of Darkness and figured that would be a good place to start as it IS meant as an introduction but I do not know how to start past that.

My problems are a bit many fold.

1) I have no clue which ordos (if any) I should place my players. Now I know the core book says "Let players choose but this comes to-

2) I am the ONLY person who knows ANYTHING about Warhammer 40K. Which is the main reason I picked Edge of darkness, it looks like a good introduction to the game. I think one has read the Horus heresy books and another did the actual tabletop miniatures way back when (And he didn't do much with the marine side of things) but other than that I am the only one with full knowledge of the universe as a whole. Part of me wants to simply go a little of each and see what they spark to and just give them an inquisitor who sides with that particular ordos. Would this be wise?

3) I know this might be helped a little when the ordos is picked but I have no idea how to properly create a long running main villian(s). These guys are used to playing pathfinder and D&D as I have mentioned above so they are going to expect a "Main Final Game Boss" type person. If this is not plausible how can I sate their beliefs without letting them down on the possibility of taking down something major when they get up there to the highest ranks?

As far as #1 and #2 go, their Inquisitor can be primarily unaligned with any major Ordos, or only loosely affiliated with one. Besides - even though an Inquisitor may be affiliated with one Ordos, that doesn't mean they're going to ignore activities that they discover, even if a report of such activities being filed through the Arbites/normal channels to request Inquisitorial assistance would get an Inquisitor from a different Ordos.

IE, an Ordos Malleus Inquisitor is not going ignore a Xenos-worshipping cult or Xenos-infiltration that they discover while pursuing a different cult. Nor would an Ordos Xenos Inquisitor ignore a Chaos-cult they learn about through investigating the Cold Trade.

As for #3 ... not everything will necessarily feed back into a single Final Boss event. There will be lesser Bosses on the way up the ranks. And, for that matter, as you get to higher ranks, you'll get assigned the higher-level, harder, more dangerous investigations that won't necessarily be connected to your prior investigations.

If they like Malleus-type stuff, a suitable end-game boss type event would be a cult trying to summon a major daemon or a major daemonic incursion. Even if that cult isn't really connected to much, if anything, else that they've done.

If they like Xenos-type stuff, maybe a run-in with a high-grade Eldar retinue or they track down the source of certain xenos artifacts and it's a broken Necron Tomb, or an advanced genestealer infestation with lots of purestrains and a broodlord or two. Or it's some other xenos race.

If they like Hereticus-type stuff, maybe there's an Apostate Cardinal or planetary governor who's about to secede from the Imperium that they have to stop. Or they encounter/have to track down a powerful rogue psyker or mutant who's stirring up mutant cults or something.

Personally, I'd say if you don't have a single long-running main villain, I'd say have multiple shorter-running villains, who are maybe in some sort of contact with one another, whom you can loosely link together - maybe they're not all working together/for the same person, but maybe they're trading some degree of information/resources/goods/etc with other people/groups on the list. IE, maybe group 1 is buying weapons from group 2, who is selling drugs to group 3 who is supplying muscle to harass group 4's rival, group 5 who are secretly being manipulated by group 6, etc.

Also possibly worth a look if you have it, would be some of the Nemesis Path stuff in Rogue Trader: Hostile Acquisitions.

Something else that has been bothering me a bit.

Looking through the Dark Heresy stuff and especially with Edge of Darkness I feel like my group might have a hard time overcoming the fact that this is indeed NOT Pathfinder and Dungeons and dragons. They are NOT the hero and as the book says: They aren't doing this for glory and gain. They are doing it because they must if humanity is to survive another day.

A lot of them might find this problematic and a bit hard to wrap their heads around. I would like to explain this to them before we play so they can have fun while still being "in character"

Also the game seems to be balanced against the players at the start. Even in edge of darkness some of the more real battles are set to be against the players. Is there a good way to explain this to them BEFORE I play to help them understand that it is the games balance setting and not me being a **** GM (because we all have dealt with a particularly poor GM who did that once before and I want them to understand that I'm actually running the game as is and not being cruel)

Okay Kai-chan here's what I can give you:

1 & 2) Like Javcs said: You won't be able to straight stick with an ordos as everyone pretty much follows everything. Throw your players into a little of each after edge of darkness: Go after some minor daemons (pink horrors are usually a win, match one for each player as they split in two after being defeated so to keep even unless they are at a rank higher than 3), Then send them on a raid against some xenos (dark elder work perfectly OR if they are more of a diplomatic style do a minor negotianion with the water caste of Tau) and finally throw them after a heretical cult. The edge of darkness set works best with this. IF the heretik gets away at the end send them after her or if she dies send them after her cult.

As for introductions: Edge of darkness is a great introduction to this. Feel free to explain as you go what they see and experience. If they have any other knowledge of any other science Fictions use those as comparasins. I once explained the hive world of scintilla is a darker more violent version of Coroscant from Star wars. Let them ask questions and take time. You'll find doing this for their first few quests will help them pick up faster when the questions they ask are going to have to be majoritively to keep them alive and not be information about who where and why.

Inquisitors can be found in the Corebook if you need help thinking of one. Pick one that goes towards the player's views. If they like to jump in at the slightest clue of corruption in a place of power then maybe Astrid Skane who hates corrupt nobles and is slightly radical. For a more calmer mellowed out inquisitor Zerbe might be better but as the head hancho of the inquisition cabal in the calaxis sector you might want to make sure your players know what they are getting into with him because as the saying goes. Great power, great responsibility.

3) Again... You probably won't find many single people to be a "FInal boss" But ​ you will find it isn't main people who will make up the bosses but the orginizations. For example with edge of darkness. The Heretik Churgeon who is the final boss of that campaign didn't just appear out of nowhere. And people like that are usually (especially in the grimdark) working for someone else. Who was she working for and why did she want those experiments done? That's a good first start.

4&5) As for your problems with the hero complex and showing them the game balance I think (since I have played Dungeons and dragons )​ that the best way to explain is something along this line: In dungeons and dragons when you are level 1 you are believed to have JUST graduated wizard college, left your fighter master, broke off with the thieves guild etc and have several years under your belt of experience in life to keep you alive. You know how to fight, you know how to survive.

In dark heresy this is not the case; You are a random person pulled off the street, shown a VERY brief explination on how a bolter pistol works and told not to shoot yourself. The only ones who might have more experience is a guardsmen or an arbitrator who would have just left basic training. You all literally are taken off the streets by inquisitors and thrown together. Your survival rate at the beginning isn't going to look good. WHat you also should stress is how much at this point they will need EACHOTHER to survive. The balance isn't in the stats its in the fact that you have several players vs the world. You all are the only think keeping humanity safe for one more day. You aren't doing this because you want the glory. You do it because you have to. Even the space marines are not known by their names. They are faceless men who wear power armor and protect people. Even the most glorious of the emperors warriors are unknown. So too will you be.

If you fear you have problems tell them you will make a character yourself and that character will be the leader for edge of darkness to keep them reigned in and help them know what to and not to do. To keep from breaking the mold with character vs dm knowledge have the players give a voice to what they think and then when you have the leader say what they will do form it on why that character would or would not do what the players say. For instance, in edge of darkness if it breaks their cover don't do it and explain why your characters would break cover. It might help them on their first mission to help them get the mindset. After that have the character move off to another group. It even gives you a contact for a hook or two later on.

With regard to picking an Ordo, it's worth pointing out that there is vastly more support material for Hereticus than for the other two combined. And every published adventure works perfectly with Hereticus Acolytes, but some require tinkering to make them work with the other Ordos (especially Xenos). So, there's that.

For recurring villains, I highly recommend keeping the Big Baddie out of the PC's line-of-sight. NPCs tend to be very squishy in this game system- every single one that I have introduced in my campaign with the intent of them becoming a recurring nemesis has been anticlimactically killed the very first time my players get within attack range- even Fate Points barely delay the inevitable...

Something else that has been bothering me a bit.

Looking through the Dark Heresy stuff and especially with Edge of Darkness I feel like my group might have a hard time overcoming the fact that this is indeed NOT Pathfinder and Dungeons and dragons. They are NOT the hero and as the book says: They aren't doing this for glory and gain. They are doing it because they must if humanity is to survive another day.

A lot of them might find this problematic and a bit hard to wrap their heads around. I would like to explain this to them before we play so they can have fun while still being "in character"

Also the game seems to be balanced against the players at the start. Even in edge of darkness some of the more real battles are set to be against the players. Is there a good way to explain this to them BEFORE I play to help them understand that it is the games balance setting and not me being a **** GM (because we all have dealt with a particularly poor GM who did that once before and I want them to understand that I'm actually running the game as is and not being cruel)

Well, as for them not being the "Heros", they have been recruited by the secret police of the 40k universe think like,

https://en.wikipedia.org/wiki/Stasi

While it is a force for Good - Inquisition , they still should work in the shadows especially at the lower levels. Now higher level you could have a Witch Hunter with all the showmanship and pop from 1 will bring.

And yes the battles might be against them and unless you have some "background" that all PC agree with ahead of time, this game is the 1st time this "team" has been assembled "off the shelf" into a team. They are rookies, rank amateurs at this game. Hopefully they will survive this game, learning what this new life can bring to them and more so what they need to survive. When we ran this game, my GM added in more gang members but not all were working for the same master. I beleive we resupply off 1 raiding team and had a memorable scene where 2 PC were surround by low level gang members armed mostly with melee weapons and they having just handgun. And 1 PC asked the other Sister Lucy Dark who is a SOB of the Order Vespila http://warhammer40k.wikia.com/wiki/Order_Vespila what the effect of fragmenting bullets have on human body at close range. She got 3 levels of success and used small words to discribe the effect of the tunneling though the body, which acted at Intimidation check and all but the "leader" failed and ran away.

The other thing there are times and places that the new team can pick their battles and select the battlefield where they control the field of battle.

Also your team faceman is more important in this game then combat monster, as they can help moderate people responce to to the team.

There will not always be a BIG BOSS Fight, there is in this game but by the time we got to this one our team was wounded and "It" got away. Now if they finish this game there is a follow-up module that was a fan written, and well there a boss fight in it that not a BIG BOSS but they are helping their boss gain info.

And I would not have them meet their Inquistor right away, instead have them work for "an Interrogator" and they are 1 of his field teams until well you know what they want to work against. Then they can meet the "Boss"