Here, right?
http://dom3.servegame.com/wiki/The_Gift_of_Kurgi
Insanity should be 10 to start, then +2 per turn, I think.
Horror Marking is rapid in the sense that it's 7 times the rate of a lightless lantern, and if you have low Defense, you'll get more marks the more you are attacked. But it's still just a base 20%.
Make sure to send a scout in wherever you're attacking, so you can take of any expensive gear, in case guy goes crazy and you think he's going to get killed.