Hydras are large, dangerous magical creatures. They typically can grow up to 10 meters in length. They have eight heads and possess great magical resilience and regenerative capabilities, especially in their heads. Even if a head is completely removed it will grow back in time.
Zorian concluded that a single mind controls the other minds (located in the heads) to a degree.
A magically enhanced hydra guards the imperial orb. This hydra is at least twice as large as a normal hydra and possesses multiple magical abilities that hydras ordinarily cannot learn, including the ability to teleport. Zach, Zorian, Damien, and their party manage to kill this hydra. During the battle one party member was killed, another lost an arm to venom, a third had both legs broken, and Damien's supposedly unbreakable divine mirror was shattered.