A hydra is an extremely large and powerful, dragon-like creature. They have bulky bodies and no fewer than eight heads, and each time a head is severed, two new will grow back. There is always one head that governs the others, which has to be killed in order for the hydra to die.
A hydra always has at least eight heads at the end of as many serpentine necks. The draconic heads are roughly the size of coffins, but they differ slightly in size and appearance.
Intrusion of the Dragon Temple
When the Knights of the Dawn trespassed into the Dragon Temple at Wyrmroost with the intention to steal the key to the vault at Obsidian Waste, the hydra Hespera, being the first guardian of the temple, attacked and trapped them between herself and the second guardian, Glommus. During the brief fight, Hespera's governing head was severely injured. Later, the dark dragon Navarog engaged her in combat. Hespera put up a good fight but was ultimately slain.