So I decided to take a little inspiration from the wheel of time rpg book. I allow the sorcerer in the party to have the ability to make a heroic effort and push himself to cast more spells than he normally can. However each time he does he has to make his saving throw or pass out. The saves get harder based on how many he has cast and what level they are.

Now for the fun bit. Each time he makes a heroic casting I roll some dice and take away a bit of his sanity. The catch however is I haven't told him or the other players this. "How can that work?" I hear you cry. Whenever a player needs to make a perception check I roll it behind the gm screen, then hand out a note to each of the players. Some are blank because they notice nothing. Some have details of some subtle thing they spotted. This leads to role play where they have to communicate what they saw without alerting others that they've been noticed. It's hilarious seeing then try to talk to each other by eyebrow movements alone. Trick is, the spell caster has been hallucinating lately and his notes are filled with lies. This has come real close to causing party infighting twice already. Next I'm going to start messing with his sense motive checks if he keeps over casting. Best part is no one at the table seems to have figured out what's going on. Some days I love being an Evil GM.