Hydra

Hydra · Lernaean serpent — Multi-headed mythical beast

The Hydra (Ὕδρα) is Greek mythology's most famous multi-headed monster, dwelling in the swamps of Lerna near Lake Lerna — hence its precise name 'Lernaean Hydra.' According to Hesiod's Theogony, born to the monstrous Typhon and Echidna, with nine heads (varying by tradition: 7, 100), the central head being immortal. Its most terrifying ability was that when one head was cut off, two grew back in its place — an absolute opponent that could never be defeated by simple force. The target of Heracles's second labor, Heracles defeated it only with his nephew Iolaus's help, immediately cauterizing each severed neck with a torch to prevent regrowth, finally sealing the immortal central head beneath a massive boulder. Its blood was used to coat arrows as eternal poison.