There are several monks that lost faith or were lured to the dark side, but the dark monks form an own secret order whose goals lie in the shadow. Not much is known about their agenda or where they have come from. The official brotherhoods of monks deny any knowledge about this special order. It is commonly assumed that these monks serve some evil power since they react hostile to most people and attack them on sight. Their fighting style clearly indicates a training in martial arts and they even use a small array of spells of which some, like draining of life-force, point to a darker purpose of their order.
Battle in the Cathedral, where the Dark Monks has their main lair.