 Apollodorus, who also mentions the theft of Helios' cattle by Alcyoneus, suggests a mother's revenge as the motive for the war, saying that Gaia bore the Giants because of her anger over the Titans (who had been vanquished and imprisoned by the Olympians).Seemingly, as soon as the Giants are born they begin hurling "rocks and burning oaks at the sky".There was a prophecy that the Giants could not be killed by the gods alone, but they could be killed with the help of a mortal.