A Hammerhead Yak is a type of animal similar to a Hammerhead shark, but shaped more like a yak. They are capable of surviving boiling lava, as one was seen jumping out of a volcano, and later out of the Earth's core. They occasionally appeared to prevent a Boneknapper from killing Gobber. Hammerhead yaks can speak, but they do not speak often. The only line ever said by the hammerhead yak was "deploy the yak." It's first appearance was The Legend of the Boneknapper Dragon along with the Hammerhead Whale.