Heracles's twelfth labor took him into the underworld to retrieve the multi-headed guard dog Cerberus. When he entered Hades's palace, Persephone welcomed him with open arms. As they were both the children of Zeus, she called him brother. Some say she hugged him so hard that she broke his ribs, which is interesting considering this is Heracles we are talking about. She was ready to give him anything he asked for.When he asked to take Cerberus to the above world, Persephone agreed. However, the dog was her husband's, and she needed to ask his permission before giving it away. She sweet-talked Hades into helping her brother. Hades told Heracles that if he could overpower and control the dog with his barehands, he could take him. Persephone also agreed to let her brother return Theseus to the above world.Heracles managed to pull Theseus free from a rock, though he could not free Pirithous who had sought to kidnap Persephone. Despite Hades's doubts that it could be done, Heracles also overpowered Cerberus and took both the dog and the king of Athens to the world above. He quickly returned Cerberus, however, after proving his point.