The Inu Inu no Mi, Model: Canis Ferox is an Ancient Zoan-type Devil Fruit, that was eaten by Mest. This Zoan fruit allows the user to take the humanoid or full form of the extinct canis ferox, somehow resembling a werewolf. However, because Mest was a test subject in G-4, the chemicals and substances injected in his body led his hybrid form to gain black fur and horns, leading some people to confuse the Devil Fruit's true ability. This change was due to the intervention of the chemicals in the wavelengths of transformation, acting as a failed Rumble Ball.