The Godess Hera, determined to make trouble for the Hero made him lose his mind. In a confused and angry state, He killed his own wife and children.
When He awakened from his temporary insanity, the Hero was shocked and upset by what he'd done. He prayed to the god Apollo for guidance, and the god's oracle told him he would have to serve Eurystheus, the king of Tiryns and Micenae, in punishment for the murders.
Apart of his sentence, the Hero had to perform Twelve Labors, feats so difficults that they seemed impossible.