In my upcoming Deathwatch adventure, players are going to be thrown aboard a Chaos Space Hulk, where salvageable Gellar fields will be few and far between. What impacts should the Warp have on characters?

My thoughts were to have the Warp work to corrupt psychic powers (my group has two Librarians....) in a variety of ways. I was thinking of having players roll d%, where

1-25: The ability functions normally

26-50: The ability loses or gains 1d5 Psy Rating

51-70: The ability functions as one level lower than intended (ie Push becomes Unfettered, Unfettered becomes Fettered, Fettered fizzles out)

71-90: The ability functions as one level higher than intended (ie Fettered becomes Unfettered, Unfettered becomes Push, Push doubles effective Psy Rating and invokes automatic Perils of the Warp)

91-100: Automatic Perils of the Warp, roll twice and use the worse result (determined by the DM)

Additionally, I was thinking of having the Warp limit or otherwise restrict the use of Fate Points, but I'm not sure how to implement this. I have a few ideas, such as players counting as having one fewer Fate Point, being unable to 'spend' Fate Points (only burn them), or spending Fate Points angers the Warp, causing a chance at summoning daemons to you.

Finally, I was thinking of inflicting 'Warp Madness' on the characters, where every day players suffer 2d10 Insanity Points and 2d10 Corruption Points. I wouldn't make it so high, except that I know the group has an Apothecary with an ability that reduces either Insanity or Corruption points gained, can't remember which.

So what are your thoughts? Things to change? Things to remove? Things to add?

If they are in the warp without a gellar field they will die in short order, barring a miracle. Period.

If the Gellar Field is intermitant or not covering the entire ship this has potential.

Yeah needs to be flickering gellar field or something, bear in mind that just looking at the warp is a fear 4 check, they will very quickly go insane just by opening their eyes, being immersed in it is almost certain death, and then if they survive they will be executed as the only way they could have survived is by being heretics.

as for the mechanics of the actual rules I think they look pretty good just be careful as you have drastically increased the probability of just popping your librarian out of existance, make sure he knows that drawing psychic power while inside the warp is VERY dangerous

Maybe I didn't make myself entirely clear: there are areas of the Space Hulk with functioning Gellar Fields, and more areas with salvageable fields, but the majority of the Hulk is open to the Warp (being a Chaos vessel). I was additionally thinking of granting the Kill-Team access to suits of sanctified Artificer and Terminator Armour for this mission to increase their odds of survival.

Fair enough, I would say on the subject of warp madness maybe do 1d10 corruption and insanity per day from being on a chaos ship, 1d10 extra corruption and insanity per day if the gellar field they are presently in is not running at full capacity. but if they are in the open warp give them 1d10 insanity and corruption every round basically. Sanctified armour covered in hexagrammatic wards would partially mitigate this. I know it is not nice as a mechanic as it will very quickly cause every pc that steps outside a gellar field to become corrupted, but I think it accurately reflects what the warp would do to a marine. Also fill the non gellar fielded sections of the hulk with all manner of nasties, daemons, spirits, zombie crew members etc. Then you can have good moments of "theres an inactive gellar field projector on the other side of this door... and just a short sprint down the corridor, someone is gonna have to go in there and turn it on, but its surrounded by the reanimated corpses of the crew members"

Also remember that chaos ships are often controlled by daemons that have been summoned into the control systems of the ship, kindof like evil machine spirits. Might want to have an encounter with the maintenance daemon trying to lock them in sections and kill them in various ways, flooding the chamber with liquid nitrogen etc. try to fit in a bit where it herds them into a garbage disposal unit and tries to crush them

As an additional thing you might want to think about if a player does hit 100 corruption or insanity turning them into an npc that is either a full on chaos marine or just so nuts he cant tell friend from foe respectively

[edit] I think I have been kind with the numbers of corruption there. if it were anyone but a space marine I would probably have the character's mind be instantly broken and their body possessed by a daemon by entering the warp unshielded [/edit]

Consider using the rules for the Primarch's curse discussed under insanity, even just as a temporary affliction while on the Space Hulk. This would be much more interesting than simply throwing gobs of numbs at your players and telling them their chracters are rapidly becoming unplayable. The objective is to keep it interesting and making each of the players role play their various curses to the hilt is a much more interactive way to go. Obviously the usual corruption and insanity point risks should also exist, but Space Marines board hulks whenever they show up because they might be occupied by a threat or have extremely valuable stuff in them, Space Marines wouldn't do this if it was always a one way ticket to making more CSMs. The same goes for the librarians, having things effect their powers is all good, but they should get some kind of warning if you are inflicting automatic worst of two rolls perils and such on them, and any player with a desire to see their chracter through the adventure would just stop using psychic techniques altogether, which sort of defeats most of the point of being a librarian. I would try to emphasize fun and memorable over punishing and limiting if I could. It is 40k, and you don't want to lose the grimdark feel, but DW is about a rather heroic bent of PCs and it is still an RPG, you presumably want to have fun.

I agree with everything Togath said, with the additional caveat that fate points are intrinsic parts of the charachters and very little if anything to do with the warp itself. Only allowing players to burn fate and not spend fate points could also be seen as being excessively heavy handed.Everything else sounds great and lots of fun

Being in the warp in a region of a ship with a non-active gellar Field is bloody dangerous, but survivable. The twisting effects of Warp Exposure are not always swift and can be kept at bay by other means (the 13th Great company have successfully done this as well as technically the Thousand Sons. Of the two 13th are probabley a better example :-) ).

The Gellar Field performs only a couple of functions really. It keeps daemons from getting Into the Ship and allows the veseel (which is a chunk of realspace) to not be effected by the twisting influence of the open Warp. Anything with a soul (basically a living creature, usually sentient) is a beacon to daemons and psykers are big blazing HERE I AM signs. If you fail to go Insane or become completely corrupt by first witnessing the Warp then you can survive in it for long periods of time (unless you get eaten by Daemons or other residents). Marines (along with Navigators and psykers as well as a certain few others) are some of the very few with the mental and spirtual fortitude combined to resist the effects of the Warp for durational periods.

To be honest with you as a GM I wouldn't touch the Warp with a 10 foot barge pole as it really just complicates a lot of things.