Hera was still angry at Hercules. One day she sent a madness on him, so that he went crazy. He was so crazy that he killed his own children, and also his wife Megara.
When Hera let Hercules come to his senses, he screamed, "What have I done?!" He needed to find some way for the gods to forgive him for this terrible crime. He went to Delphi and asked Apollo what to do. Apollo said the gods would forgive Hercules if he did twelve hard jobs for Eurystheus (YER-iss-THEY-oos), the king of Argos - we call these the twelve labors of Hercules.