Shuumatsu no Valkyrie - S02E14

Every 1000 years, the Gods' Council assemble to decide the fate of humanity. After 7 million years of human history, the gods come to the decision that humans are irredeemable and must be extinct. However, the valkyrie Brunhild proposes that humanity must have one last chance to prove their worth and the gods agree on holding the battle of Ragnarok, with 13 notable humans from across history against 13 of the most powerful gods engaging in duels to the death, with humanity being spared should their side achieves 7 victories in the competition. To even the odds, each human is granted the assistance of a valkyrie who transforms into a powerful weapon tailored for their combat style called "Volund", at the risk of losing her life if the user is killed.