Lernaean Hydra

The Hydra was a monster and daughter of Typhon and Echidna. She had the ability to transform from a small girl into a three-headed serpentine creature. Each head, when severed, would spring up as two heads. (Hercules and the Amazon Women; HTLJ: "Cast a Giant Shadow")

As a child, she was known for being a good knitter. This would not last, however, as she became a servant of the goddess Hera. (HTLJ: "Cast a Giant Shadow") She would go on to devour many on the road to Corinth. (Hercules and the Amazon Women)

In one of his early journeys, Hercules and Iolaus discovered the Hydra near a temple to Hera. After an intense battle, they destroyed her by setting her on fire and ending her killings. (Hercules and the Amazon Women)
 * "Hercules on Trial" implies that "the Hydra problem" occurred near the town of Eubola. It is possible that this is a nearby town in Corinth.

Because of this, and similar incidents, the Hydra's mother, Echidna, swore vengeance on Hercules. (HTLJ: "THe Mother of All Monsters")

This incident would be immortalized as one of Hercules' epic feats. Iolaus himself was affected by the Hydra, telling many of his defeat, with Hercules' help, of the Hydra. (HTLJ: "The Wrong Path"; "Pride Comes Before a Brawl"; "Cave of Echoes") He also had at least three nightmares where he was devoured by the menacing Hydra. (HTLJ: "[War Bride]]")

When Hercules lost his memory, Iolaus tried and failed to remind him of the Hydra and the Minotaur. (HTLJ: "Prince Hercules") Many other people assumed that Hercules would be an awe-inspiring figure, based on his defeat of both the Hydra and a cyclops. (HTLJ: "Descent")

Petracus considered Xena to be just as much of a metaphorical "monster" as the Hydra, Nemean Lion, or Stymphalian Bird. (HTLJ: "The Warrior Princess")

Backround Information
The Hydra's human form was portrayed in its one appearance by Rose McIver. She later went on to portray Hercules' daughter Ilea and the young girl Daphne in "Little Problems" (which contains a Hydra mention).

The Hydra was not known by name by Hercules and Iolaus when they faced it, but was likely only known by reputation elsewhere, such as in Eubola.

The Hydra was the first monster to be shown in an HTLJ production and was used in the opening credits to the show.

Appearances

 * Hercules and the Amazon Women
 * HTLJ: "War Bride" (dream sequence)

Other mentions

 * XWP:
 * "Hooves and Harlots" (If it looks like a hydra, and moves like a hydra, it’s a hydra.)
 * "The Prodigal" (Hey! Hydra-heads!)
 * "Girls Just Wanna Have Fun" (And a hydra makes a good pet.)
 * HTLJ:
 * "Hercules, Tramps & Thieves" (It's Hera! Would you believe Zeus?  A fliying Hydra with the runs?)
 * XWP:
 * "Little Problems" (Ride her like a hydra!)
 * HTLJ:
 * "Full Circle" (You know, you may be able to sell that kind of Hydra dung to Evander...)

Background Mythology

 * See Wikipedia's Lernaean Hydra for full information.

In classical mythology, defeating the Lernaean Hydra (Greek Λερναία Ύδρα) was the second of Heracles' twelve labors. It lived near Lake Lerna and its blood was poisonous. This poisonous blood was used by Heracles on arrows that ultimately killed the centaur Nessus, which in turn killed Heracles (a version of which is shown in Hercules and the Underworld).