Yeah crushing weapons are probably all arond best anti-undead weapons, but really I never have any problem with a greatsword, but I think a great hammer probably would do more damage, fire essence on the weapon helps immensely.
flaming arrowes and fire spells from a distance are better though, why risk getting hurt, Mage has fire spells anyway Flare usually, Rogue/Ranger has fire arrows by that time a few at least, and I give my fighter some fire spell scrolls so no one has to get close to that damnable poison.
I love when I get to torch Rob the Zombie...I also really like the legless Zombie's, this game has many charms.
