Hydra

The Hydra was a vicious monster, presumably sent by Kronos to kill Percy Jackson and his fellow questers in The Sea of Monsters. It was large and lizardlike, with a long neck and several heads. It had many rows of razor-sharp teeth, its hands were clawed, and had a tail. According to Annabeth, it sprouted another head every time a Monster Doughnut popped up. Percy initially tried to defeat it by slicing off its heads, but suceeded only in making more heads. percy and Annabeth were saved by Clarisse when the Hydra's heads were lit aflame and burnt off by cannonfire from the USS Birmingham.