One day, the god of all gods, Zeus had a baby with a mortal, Hera. His name is Hercules and he was a half god. HIs mother, Hera, became jealous that Hercules was born part god and in spite, tried to kill him. All of her attempts failed and in order to protect Hercules, Zeus sent him to live with mortals.
Hercules was raised and taught well, he was noble and responsible. He eventually married and had a couple kids with his wife. Since he was very large, he stood out among everyone which led to Hera finding his location. Hera was a mortal which stood no chance against a half god, so she decided to use evil magic. Her evil spell caused Hercules to murder his family and when his conscious would return, he would realize what he did.
When Hercules saw what he did, he knew that murdering his family is not something he would do intentionally. He went to talk with the Oracle and when he described what happened, the Oracle knew Hercules did not murder his family on purpose. The Oracle knew it was evil magic and was probably the works of Hera but also knew that Hercules would never forgive himself unless punished. So the Oracle told Hercules to go to his cousin, Eurytheus, where he would receive twelve tasks to complete. Hera had sent spies to watch Hercules and discovered what the Oracle told him to do.
Hera decided to go to Eurytheus before Hercules got there to try and convince him that Hercules was trying to steal his crown. Eurytheus believed Hera and she also told Eurytheus about the twelve tasks. The two of them came up with what was thought impossible and would kill Hercules. Once Hercules reached Eurytheus's palace, even though Hercules did not want the crown, he accepted the challenge.