Hydra

The Hydra is a 7-headed boss from Kingdom Hearts II. Hades sent the Hydra to destroy the Olympus Coliseum and kill Hercules. Hercules had to fight it in the Coliseum and thought he had defeated it. It in fact was not finished off 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 and chivalry, making him later fall prey to the plans of Hades.

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.''

Battle
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 around the battle 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

 * In the Japanese version of the game the Hydra spews green blood when a head is cut off, similar to the movies. However in the American version it is replaced with purple smoke, yet the green blood is briefly seen in the the Hydra's first cutscene against Hercules.