I am new here and this has probably been covered. I like for the darker horror aspects to be in my Deathwatch games. I want corruption to be a very real threat - one that the player feels they need to keep in check, especially for psychers and librarians. I mix Dark Heresy and Deathwatch freely. Not as much Rogue Trader simply because I want the characters to have a deep connection to the Emperor.
SOURCE OF CORRUPTION POINTS
One of the main ways to get corruption points and for that matter insanity points and chances to really mess things up is with Psyker powers… both from the Psykers in DH and the Librarian in DW. Another way is moral threats - some detailed in Dark Heresy.
Psychic Ability Differences: In Dark Heresy (DH) if you roll a 9 to manifest the power you get Psychic Phenomena. In Deathwatch, a Librarian because of the fact that they are more powerful and have more control, they must roll doubles when using at full power… they can also push if they want to. It is more dangerous for a non-librarian to use psyker powers.
THE THREAT OF CORRUPTION
Now I like to use the Malignancy Test (in Dark Heresy) for both the Librarian and all other psykers in the game. It makes corruption a very real threat. Normal psykers will become corrupt faster than a librarian due to the nature of the Librarian having more control over his psyker powers. Also, mutation should be a very real threat (also found in Dark Heresy).
Every 10 points roll on the Malignancy table (even for Deathwatch Librarians)
THE TAINT OF CORRUPTION
Because I try to allow a Librarian and other Psykers to cleanse themselves of corruption, I make it more dangerous to have corruption. In Dark Heresy there is a Mutation check. Every 30 Points the corrupt must make the Mutation check.
The removal of corruption should never come easy. Here are ways to cleanse corruption from your soul;
1. Not gaining any corruption for a full mission will cleanse 1d5 corruption. Corruption does not go away with time, it wears away when you chose not to use the powers that can corrupt you. Sometimes even then an outside force can prevent you from cleansing yourself.
2. There are places of Hallowed Ground (in my games). Now, these places are very rare. Places where, it is said "the emperor stood at peace" which is probably some very rare places. Once at these places you must atone for your sins (Focus Check to Manifest a power). You will be cleansed of 1d10 corruption and 1d10 for each degree of success. You can never use the same place again, or any place even remotely close (within the same star system).
3. Relics are very powerful, so long as they radiate with the light of the Emperor or some other power that is very good (some ancient eldar relics have the same power). The major problem, these relics cannot be used for war or the making of war. Taking ownership of a relic such as this and using it to meditate upon (focus check to manifest a power) you will be cleansed of 1d5 corruption and 1d5 for each degree of success. The same relic can never be used again and you may never use the ability that relic would normally grant.
4. There are other ways but the paths are hidden for most because many ignore corruption until it is too late.
IT AFFECTS EVERYONE
While I really focus on the psykers and Librarians… these rules effect everyone in my games from the Devastator Brother to our ever watchful Apothacary. They must all watch for moral threats. Even some choices they can make will bear corruption penalties. Also, in my game you fall to Chaos - your character is mine. I don't play a character in our games, I try and really focus on being the villain or the Inquisitor or whoever… So, getting a chance to take a character that didn't try to stay on the path of the rightous falls to my hands and becomes a true threat and villain from here on out :)