Hmmm.. well first of all Valicor... isn't it Du HAST?
Evil necromancer music...hmmm
Well actually my band played (not all that well) a really cool piece at our last concert that could possibly work for a necromancer... at least the first movement (which isn't all that long, unfortunately) It starts with a really grinding chord that kinda creeps you out. But yes, the title would be a good thing...LOL. Symphony Number 1: In Memoriam Dresden by Daniel Bukvich, specifically the first movement. The rest of it is sort of modern--it's about the firebombing of Dresden Germany, and the last movement features all the musicians making sound effects of bombs dropping, people screaming in german, while the bassline still keeps the grating chord and the percusion makes explosions and general loud noise. It's really cool and I've gone on WAY too long about it... anyhow. More music...
The sephiroth theme from Final Fantasy 7 is probably some of the best villain music i've ever heard.
Just plain fight scene music that gets your energy going: the theme from Blade, and Smack My Bitch Up by Prodigy
more villainy goodness: look for various tunes from Konami games--I think the Castlevania series has a bunch of stuff online that works pretty well.
For a great CD in general for games, DEFINATELY check out Midnight Syndicate's CDs... I have Realm of Shadows and it is MARVELOUS. Such good stuff... I really need to pick up their other CDs.
That's all i can think of for right now.