Hydra

The Hydra is a multi-headed monster that is found in Kingdom Hearts II. It is one of the bosses at Olympus Coliseum.

Kingdom Hearts II
Hercules (1997)

''A legendary monster with many heads, sent by Hades to fight Hercules. If you cut off one of its heads, two more grow back.''

Kingdom Hearts II
Hades sent the Hydra to destroy the Olympus Coliseum and kill Hercules. Hercules had to fight it in the Coliseum and believed he had defeated it, but it was in fact was merely playing dead and started to destroy the Coliseum. The Hydra met its match when Sora, Donald, and Goofy as well as Phil, Pegasus, and Megara came in to help out. However, the aftermath of the battle was rather unfavorable - the Coliseum was destroyed and Hercules lost his hero's glow, making him later fall prey to the plans of Hades.

Strategy
The battle begins as Sora attacks the main head for a while. Then a Reaction Command called Vanquish appears - doing so will allow Sora to remove its head. It puts its head in the sand and three heads sprout from the surrounding area. With Phil's help you can immobilize the heads with a Reaction Command called Phil One-Two and then follow it up with Urninator. You then must defeat and Vanquish the heads before they awake.

The Hydra then pulls its neck out of the ground and shows that it has seven heads. While fighting the seven heads, you can use Pegasus to fly up to the heads to strike them with a Reaction Command called 'Pegasus Run'. Once it is out of HP, you can use the Vanquish command again. If you ever run out of HP, MP, or Drive, Megara is found at the outside the arena itself, hiding on the very left side of the arena. Simply run around the area, and will toss you what you need.

Hydra is capable of summoning dark orbs, using lightning, and using blue fire similar to Hades. At the end of the battle you get Thunder and after the cutscene, Hero's Crest. If you die, don't worry - King Mickey will be able to help you.

Trivia

 * Like the movie, the Japanese version of the game has the Hydra spew green blood when a head is cut off. In the American version this was replaced with purple smoke, though the green blood is still visible during the first cutscene of the Hydra.