How does one deal with characters that hit either the 100 Insanity or Corruption Points. (Make them an NPC, sure). But I'm after suggestions on how to roleplay these in either some form of descriptive cinematic or something similar so that the character becomes an NPC to some degree and potentially a major villain of some sort.

The biggest problem I had was dealing with one of the NPCs the party had that survived with them through the entire Haarlock campaign until the last adventure and on Mara (due to a psyker's power) hit 100+ Corruption Points. I've applied the suitable mutations and malignancies for this NPC. But am now dealing with the roleplaying considerations, he was a good guy but now he's a raving bloddlust hungry murderer (i guess I gave him up to Khorne).

Normally I would have got them to attack the party at this stage, however they keep getting him into these great big violent murderous fights, so have him sticking along with them. Any other suggestions on how his behaviour and moods should change? (and yes, he survived demonic possession, and 2 mind swap perils of the warp with the party psykers)..

Yamir Ke'Shark said:

Is the player still controlling this character, or are you? If the character is supposed to become an unplayable NPC when he's that far gone, then he should be taken away from the player immediately. If you're controlling the character, then how long he stays with the party is entirely in your hands. If you want him to turn on the players, then make him turn on the players. In the middle of one of these big violent murderous fights, if you like. If he's really that crazy with bloodlust I could easily see him losing track of who are his allies and who his enemies in the middle of a brawl.

If he has dedicated himself to Khorne, then perhaps he would start insisting on going someplace he can properly worship his new God. If the party agrees to take him to Chaos space, he can betray and attack them once he joins up with his Chaos bretheren (which should really not come as a surprise to anyone.) If they refuse, then he can attack them and run away when he sees an opportunity, only to return at some point in the future as a villain when the party goes up against Chaos forces.

Maybe Hannibal Lecter-ize him? Have the character 'know' something or discover something about the Tyrant Star, something that makes keeping them alive, in captivity instead of taken out.

at 100 IP/CP I think perhaps they should gain a enw disorder- the 'big one' , so to speak. A mania or malignancy so great, that it may noy instanly NPC-ise them, but at very least, it should make it clear that retirement is ahoy. It might happen instantly, in a sudden snap, or it may take time to unfold. Perhaps this character is utterly unable to curb their lust for blood. They hack at corpses long after they're dead, they are utterly unable to take anyone alive, attacking with only their most ferociously lethal force. Perhaps they may fall into a frenzy and never leave, perpetually frothing and foaming at the mouth, having to be restrained. Maybe, once the combat starts, they are no longer able to distinguish friend from foe. Maybe they realise that no one is an innocent by the standards of the inquisition, even-maybe especially- the inquisitors themselves...

But, while it does provide for an epic resolution, i don't thin the fully insane or corrupt character should always return as a villain, sometimes that just won't suit the tone of the plot. The character who hits 100 IP may just become catatonic, or a gibbering wreck for the rest of their days.

This guy looks like he might snap and become a serial killer.

Maybe he might manifest an alternate personality while he sleeps who does some extra killing, since there can never be enough.

Maybe the character loves carnage so much they hack at their own flesh, crippling and maiming their libs irreperably.
Maybe they remain sane on some level, but now have a voice howling in their ears, constantly telling them to kill, so much so that it drowns out the words of anyone around them? This may be accompanied by visual hallucinations as their insanity takes the form of an external tormentor, something or someone conjured up from the very darkest pits of the character's imagination. Remember, we're all afraid of something, and, even in 40k, the demons within one's own head can be every bit as fearsome as the daemons without...

Since this is a "special" NPC that has been with the team for several years (special enough to use IP and CP!) I would play things up over time instead of a sudden "snap". Since he has fallen to Khorne his subtlety is not going to be that drawn out, but betrayal and sacrifice is so much sweeter (and thus pleasing to Khorne) if he times the revelation of his new loyalty at a dramatically appropriate (and inconveinient) moment! Since they continue to get into bloody fights he can sate his bloodlust.... for now! Then when they get into the dramatic and epic confrontation with the atory arc's "big bad" have blood-boy wade in: Start off having him inflict some truely gratuitous bloody kills on the enemy and then once the tide shifts towards the Acolytes he simply begins killing anything that is within chainsword's reach, friend or foe alike! Should he somehow survive the battle you can then have one of the surviving Acolytes deliver a pathos-filled execution to their once-ally. Good stuff!

As a Pysker s/he's more likely to accepted by Tzeentch than Khorne, and my interpretation of Corruption is not a raving pyscho it's that he's fallen to his own needs and wants. His/her Ego is now running things in his/her brain, and will do "anything" to get them no matter how depraved, but some things still take planning. In this state the character should definately be in your hands unless you intend to write some sorry on the character crossing that boarder and fighting it's way back, perhaps with the help of the other players, as a player can spend XP to reduce IP/CP it is a possiblity.

As a Suggestion to that have the other players walk in on him/her performing some Ritual to call forth a daemon that can grant him/her the power s/he seeks, but the distrurbance in the ritual causes it to go badly wrong and the players end up running through a mind scape of the pyskers mind fighting off the corruption, Inception sytle.