Lernaean Hydra

The Lernaean Hydra or Hydra of Lerna (Ancient Greek: Λερναῖα ὕδρα, romanized: Lernaîa Húdrā), commonly known simply as the Hydra, was a serpentine lake monster in Greek and Roman mythology. Its domain was the lake of Lerna in the Argolid region, which also featured in the myth of the Danaïdes. Lerna was believed to be an entrance to the Underworld, and archaeological evidence confirms it as a sacred site predating Mycenaean Argos. In the standard version of the Hydra myth, the creature is slain by Heracles (Hercules) as the second of his Twelve Labors.

According to Hesiod, the Hydra was born to Typhon and Echidna. The monster possessed deadly poisonous breath and blood so potent that even its odor could kill. The Hydra featured multiple heads, though sources vary on the exact number. Later variations of the myth introduced the creature's remarkable regenerative ability: whenever one head was severed, two would grow in its place. To overcome this challenge, Heracles enlisted his nephew Iolaus to help remove all the monster's heads and cauterize each neck with fire after cutting it with a sword.