The Dualhead Hydra is a monster from Final Fantasy Mystic Quest, the Fiend of Fire and one of the Vile Four. It can be found in the central room of the Lava Dome. After it is defeated, the Crystal of Fire reverts to normal, and the Volcano erupts. Dualhead Hydra is later reincarnated as the Twinhead Wyvern in Doom Castle.
As with all of the Vile Four, their reincarnations, and the Dark King, Dualhead Hydra has four phases to the battle, depending on how much HP it has left. The first phase has its right head facing the player and the left facing to the side. After losing a quarter of its health, the right head is reduced to a stump. After losing half of its health, the remaining head takes over the body and its eyes turn yellow. After losing three-quarters of its health, the creature's head is lowered and the wings are left tattered.
Hydra was one of the spawn of Echidna, a many-headed serpentine monstrosity in Ancient Greek mythology. It could breathe poison, and indeed its very blood was deadly. The Hydra was killed as one of Heracles's Twelve Labors.The
- When one of Dualhead Hydra's heads is slain, the remaining head takes over the body, the neck stump of the second head vanishing. This is in contrast to its namesake, which was said to grow more heads when one was sliced off.