Eeevil ideas to use with the truly evil characters (not to be taken too seriously, mmkay?):
Skinnable human corpses! Maybe with a special tool that would be usable only by neutral/chaotic evil characters. Would require the corpse to remain for some time before vanishing so that it could be skinned.
Human skin crafting. Nothing says "Evil Necromancer" like a cape made of the skins of murdered people.
Cannibalistic cooking. All flessshh must be eaten.. Weird barbarian cannibal tribes or dark necromantic guilds with twisted eating habits. Blackguards making a raid on a town and devouring fallen comrades/killed townsfolk after the battle is over... It could even be a tradeskill. You'd get meat from the corpse the same way as in skinning, with a special knife.
These kinds of traits would really make evil characters despitable and hated among the "good" people. There could be also quests, for blackguards for example. A long and hard journey in search of the true art of death and destruction. Finally in a desolate location joining an old religion that serves the old gods, needing to feed on human flesh to survive after the initiation..
After all, people take (roleplaying) "chaotic evil" often a bit too lightly. A chaotic evil person is in my opinion a twisted, nontrusty person that is to be feared. These new traits could help to define what the darker end of the spectrum could be like. Hey, ghouls and vampires do it too!
So... BOO!
-ReiskaR
