The gods of the world—from Greek to Norse to Hindu mythology—gather every one thousand years to make one important decision: whether or not to wipe out mankind. Repulsed by humanity's selfishness, the council unanimously votes to destroy all humans. But before the decree is enacted, Brunhilde, one of the 13 Valkyries of Valhalla, interrupts the meeting to give mankind a chance at survival. Brunhilde proposes the idea of enacting Ragnarök, an event in which the strongest 13 mortal warriors fight against 13 gods in one-on-one matches. Although the trial is ridiculed by the gods, the demigod takes advantage of their pride and forces them into an agreement. However, Brunhilde herself must recruit the mightiest heroes throughout humanity's thousand-year history and guide them to victory before they meet their untimely demise.

In a shocking turn of events, humanity has won its first battle in the Ragnarök tournament—a series of 13 fights that will decide the fate of mankind. Zeus, the head of gods, sends the demigod Heracles for the next round to avenge the humiliated Greek pantheon. To face this hero loved by gods and humans alike, the Valkyrie Brunhilde decides to use Heracles' complete moral opposite: the infamous serial killer Jack the Ripper—leaving human beings unsure who they should support. Meanwhile, tensions begin to rise between various divine pantheons, and rumors of a traitor jeopardize the unity of those who want to annihilate humanity. As the line between friend and foe becomes blurred, Brunhilde will do everything she can to make her machinations successful.

Following the most recent brutal battle, the gods now hold the lead against mortals in the one-on-one tournament that will decide the fate of humanity. With three wins under the belt of the divine beings, the humans only have 10 matches left to save themselves from extermination. The Supreme God Zeus intends to take the upper hand by sending Buddha—a benevolent demigod loved by all of humanity—into the fray. In a shocking twist, Buddha announces his intention to fight for humanity. Enraged by this betrayal, the gods call upon the Seven Gods of Fortune to take Buddha down. As their battle rages on, a mysterious entity manifests in the middle of the arena, throwing the entire competition into disarray.