Kleomedes

While in the Olympic final, an ancient Greek boxer named Kleomedes killed his opponent by stabbing his fingers into his opponent's chest, killing him. There was a rule that if your opponent was killed by the fight, he automatically won. So despite surviving the fight, Kleomedes is judged loser. He returns home to Astypalaia and lapses into a deep depression and commits the first mass murder of school children after punching a support beam so hard the school fell down. All the kids died. Angry mob forms to kill him so he takes shelter in a giant chest in the temple of Athena. Townsfolk storm the temple, having to rip it apart board by board. But when they got it open there was nothing in it. People didn’t know what to make of it. So they sent people to the oracle of Delphi, who declared that Kleomedes was The Last True Astypalaian and that he be worshipped as a Demigod. That is how an Olympic boxer became a deity of fertility after murdering a bunch of kids.