In Greek mythology Zeus was the king of the gods. Knowing how useful the fire was, wanted to keep it for the gods. The god Prometheus, however, disobeyed his command, stole the fire from the gods and gave it to people. Zeus in order to punish him bound him with chains to a rock and every day at a certain time an eagle was sent to eat his liver. The torture went on for several years until Hercules (who was one of the Zeus' sons with a mortal woman Alcmene and therefore was a semi- god) passed by, felt sorry for him killed the eagle and freed Prometheus.