The Hydra, also known as Hydragon, is Kaos' four headed dragon in the console versions of Skylanders: Spyro's Adventure. It serves as the final boss alongside Kaos, assisting him in the battle, and is the most powerful of all of his Minions. Each dragon head summons forth the same type of trap seen in previous Elemental battles against Kaos' Minions.
Skylanders: Spyro's Adventure
When he was losing his second attempt to destroy the Core of Light, Kaos released his Hydra into the battle and it was powerful enough to successfully destroy the Core; its destruction was what triggered the events of changing Master Eon into a spirit (though he survived the blast) and banished the Skylanders to Earth.
When the new Portal Master and their Skylanders finally confronted Kaos face-to-face, the evil tyrant summoned his Hydra to aid him in the battle. Harnessing four of the main elemental classes, the Hydra proved to be a powerful opponent though it couldn't be fought directly due to a magical barrier that surrounded the arena. After Kaos was defeated, the Hydra withdrew back into the darkness and was never seen again.
The Hydra appeared as a storybook hazard in Book #4: The Hydra in the Spell Punk Library, where it is explained that in the distant past, the beast was a pet to Dark Portal Masters. To appease the Hydra's endless appetite, the evil Portal Masters took all the food in Skylands and dropped them into the sea where the Hydra resided. The Skylanders, heedless of the danger, dove into the underwater depths to the Hydra's lair to take back the stolen food. Despite the Hydra's relentless pursuit, the Skylanders were able to escape the beast and gave back Skylands the food that was taken from them.
- The Hydra uses the power of the same elements found in boss battles with Kaos: Life, Undead, Fire and Water. These elements are also opposite to each other.
- These elements are also the elements of the four Skylanders in the Battle Packs of Skylanders: Giants.
- It could also be a reference to the four seasons; Summer and Winter corresponding to Fire and Water (ice) for their temperatures, and Spring and Fall relating to Life and Undead for the life of plants at that time.
- The Hydra bears a slight resemblance to Dungeon & Dragons' Tiamat.
- When ever the Hydra uses one of its elemental attacks, it also summons several elemental twisters tied to the respective element used, however these don't do any damage.
- The Hydra has a blue, turtle-like shell, reminiscent both colour-wise and shape-wise to a giant Roboto-Ball.
- According to an infograph about the Skylanders franchise, Kaos rented the Hydra from the Doom Valley Evil Nature Reserve as part of his plan to destroy the Core of Light.
- There is a glitch where when you defeat Kaos, the cutscene does not appear. Castle Blackthrone disappears, the Hydra is frozen falling into the darkness and the Skylander is standing on thin air, isolated by invisible walls.
- In Skylanders: Swap Force, the Hydra is mentioned as one of the preferred minions for Dark Portal Masters in the Twisty Tunnels Story Scroll.
- Though the cover for its book in Spell Punk Library shows that its body is small and scaly in comparison to its heads, Spyro's Adventure had the Hydra being much larger, blue, and covered in golden plates for reasons unknown.