Beliar is worshipped by Orcs, Demons and even some Humans. He grants dark magic to his followers, but at a cost. He's locked in an eternal struggle with his brother Innos; the Lord of Fire.
At the end of Gothic 2: Night of the Raven, it is revealed to the Nameless Hero that Xardas has become the Chosen of Beliar.In Arcania, it was revealed that all three major gods - Innos, Adanos and Beliar - are the same entity as the Goddess. The deity had her personality split into three seperate entities, who struggled with each other.