When a mysterious portal appears in the sky, humanity unites in curiosity and fear. Russia launches a nuclear assault, but the weapons vanish into the portal without effect. Moments later, a colossal being of light emerges, claiming to be an angel sent by God to prepare humanity for a celestial war against ancient monsters and demons. This angel gives humanity an ability known as the Heavenly System to give humanity a chance to fight against the opposing armies. Years later Viktor Callaghan is inducted into the Heavenly System at the age of sixteen and he begins to climb the ranks of the army of humanity.