The irate Norse god chained her to an altar in Asgard, surrounded by a ring of eternal fire.
He decreed that only a pure-hearted man could overcome the supernatural flames and save the alluring Valkyrie.
As Barek explains, he and his only brother learned about this as little boys and craved more and more to rescue the legendary beauty as they grew older.
As it is later on successively revealed by flashbacks, Boar eventually could not resist anymore and entered the ring of fire.
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.