Skeletons, zombies, ghosts, liches, spectres, wraiths. There can be more.

Augmentation

Notable Weapons that are augmented after killing any Undead:

• The Wyrdaxe - Kills 100 Undead
• Eater of the Dead - Kills 100 Undead
• The Gearhead - Kills 1000 Undead
• Hammer of Consecration - Kills 1000 Undead
• The Death Toll - Kills 1000 Undead
• The Caliphaze - Kills 100 Undead
• The Light of Dawn - Kills 1000 Undead