Berserker is a fantasyactionhorror film based on Norse mythology. It was written, directed and produced by Paul Matthews and had its main release in 2004.
As it is later on successively revealed by flashbacks, Boar eventually couldnt resist anymore and entered the ring of fire. Hereby he suffered severe burns. Barek followed him into the fire and remained wondrously unharmed. He unchained the valkyrie and persuaded her to save Boars life. Unfortunately her bite turned Boar into a cannibalic Berserker.When their father, Viking leader Thorsson is in need of reinforcements because he is in war with the Army of the Nord, he joins an alliance with the Berserkers who are now led by Boar. Following their combined campaign they fight each other. Thorsson uses fire against the otherwise immortal Berserker Boar. Barek cannot bear see his brother burning and calls Odin for help. Odin complies with Bareks request but from now the fates of Barek, Boar and Brunhilda are interlinked by a timeless curse. ........
Source: Wikipedia