In Greek mythology, the Giants were the children of Gaia, who was fertilized by the blood of Uranus, after Uranus was castrated by his son Cronus. Some depictions stated that these Giants had snake-like tails.

Gaia, incensed by the imprisonment of the Titans in Tartarus by the Olympians, incited the Giants to rise up in arms against them, end their reign, and restore the Titans' rule. Led on by Alcyoneus, and Porphyrion, they tested the strength of the Olympians in what is known as the Gigantomachia or Gigantomachy. The Giants Otus and Ephialtes hoped to reach the top of Mount Olympus by stacking the mountain ranges of Thessaly, Pelion, and Ossa on top of each other.

The Olympians called upon the aid of Heracles after a prophecy warned them that he was required to defeat the Giants, for the aid of a mortal was needed.Athena, instructed by Zeus, sought out Heracles and requested his participation in the battle. Heracles responded to Athena's request by shooting an arrow dipped in the poisonous blood of the dreaded Hydra at Alcyoneus, which made the Giant fall to the earth. However, the Giant was immortal so long as he remained in Pallene. Athena advised Heracles to drag Alcyoneus outside Pallene to make the Giant susceptible to death. Once outside Pallene, he was beaten to death by Heracles. Heracles slew not only Alcyoneus, but dealt the death blow to the Giants who had been wounded by the Olympians. The Giants who died by the hero's hands were Alcyoneus, Ephialtes, Leon, Peloreus, Porphyrion and Theodamas, giving Heracles the most kills of the Gigantomachy.