Six-year-old Kael possesses innate superhuman strength, capable of shaking mountains with his bare hands. His mother, Lyra, a high priestess, carved a seal on his chest with fresh blood to protect him from the gods' jealousy. Twelve years later, Kael became the """"illegitimate child"""" who was humiliated by everyone in the Spartan city lord's mansion. Until the Persian envoy Xerion, accompanied by the giant Urag, invaded Sparta, forcing the city-state to submit and demanding the abduction of the grand elder's granddaughter Selene. Aristos died in battle, leaving the entire city in despair. Kael finally stopped hiding, his eyes burning with golden flames as he leaped to save Selene, slashing Urag and killing Xerion, thus winning the hearts of the Spartan people. Persian King Xerxes was enraged and personally led his army to the border. Kael led 300 Spartan warriors to the Thermopylae Pass.