Umm... For some strange reason I've been playing that each critical adds one black die for all future actions. I'm beginning to suspect that I'm being stupid because I can't find it in the rules. :-)
Can someone confirm whether I'm being stupid?
The truth is that it hasn't ruined the game or anything and it does a pretty awesome job of causing gradual degradation of the characters. I'm just trying to get better at game mastering.