I believe you're referring to Azuredge. The lich at the City Gates got killed on the first hit by that axe, in my current game.

Where do you get this throwing axe? Korgan in my evil game could do with it. I think I remember only good characters can wield this axe, is that true?

Hmmmmm...well the spell Sunray is very effective against undead, and I mean VERY effectivehowever in saying that I haven't tried it against Vampires but it does kill shadows instantly so it should do some damage.

I thank you all for your advice and wisdom. I will search for this amulet thingy and I will cast negative plane protection. I thank you and all of you have a reward........my gratitude! Since you guys or ladies told me this the vampires would be "easy as goblin pie"

Bernard in the Copper Coronet sells it, but only after you've done Hendak's quest to free the gladiators.
And you're right, Azuredge can't be used by neutral or evil characters.

I was loot... errr I mean exploring ;) the crypts in the graveyard district when I stumbled across this one with a mummy and two shadows. Casting Sunray from the Daystar, it did 50+ to 60+ damage to each of them, lsaying 'em instantly.