Dark Heresy: Dulce et Decorum est
As you play, your character may gain “Insanity Points” due to exposure to The Warp or other horrific things.
Game mechanically, you record them on your record sheet as you see fit.
When you gain enough Insanity Points, the GM will assign you some random Disadvantage related to your growing madness (usually a derangement). However, your character total is not decreased. The points gained by this new Disadvantage may be spent on improving your character in other ways (mental advantages, acute senses, psychic powers, etc. etc.)… after all… there is strength in madness.