As an act of revenge, Zeus hid fire from humankind, leaving them cold and shivering at night. Prometheus, however, out of pity stole it for them shortly after, incurring the further wrath of Zeus. Prometheus's punishment was to be chained to a rock and have an eagle (or a vulture by some variants) pick out his liver every day for eons, until Heracles slew the eagle, releasing Prometheus from his affliction. The "Theogony" text is ambiguous about whether Prometheus was freed or remained chained to the rock, but lines 615-616 are usually interpreted as indicating that he remained bound.