Every thousand years, the gods of the world—from Greek to Norse to Hindu mythology—gather to make one crucial decision: whether or not to wipe off humanity. The council, disgusted by humanity's greed, unanimously votes to exterminate all humans. But, before the decision is carried out, Brunhilde, one of Valhalla's 13 Valkyries, stops the gathering to offer mankind a shot at survival. Brunhilde recommends reenacting Ragnarök, an event in which the greatest 13 mortal warriors compete in one-on-one contests against 13 gods. Despite the gods' mockery of the trial, the demigod takes advantage of their arrogance and compels them into an agreement. Brunhilde, on the other hand, must collect the greatest heroes from humanity's thousand-year history and lead them to triumph.