Dark Side modding start question

[kbounty1]

btw this may help someone maybe, i found how to make the effects (Bleed, burn,..) dispellable : in spell.txt remove 'exception' from Dispell, and in effects.txt 'no_dispell=0' instead of 1 for each effect. You can now use the spell Dispel to remove these effects from your creatures.

There are still 2 things i can't find if anyone knows :
1) the critical hits damage multiplier file, or is it hardcoded?
2) and how to make Black Dragons immune to plague! from necromancers. I think i tried everything with the Necromant.atom, spells.txt or 'infection' in effects.txt. "nfeatures=plant,mech,golem,demon,pawn,boss,blackd ragon" does not work..