A Lich is an undead wizard whose primary practice was necromancy, their powers became so great that they could revive themselves with their soul and intelligence intact upon death. Unlike normal undead such as ghouls & skeletons, Liches remain in full control of themselves as well as keep their human intelligence. Liches have extreme amounts of magical abilities, and can usually raise the undead at the wave of a hand.
Liches in Barony, however, summon demons, can fly across pits, wield swords, and create unnatural darkness. There are a total of 3 in the game: Baron Herx, Orpheus, and Erudyce, all 3 are tough boss fights to beat.