Undyne is a incredibly strong enemy that kills any humans to enter the underworld. She knows only too destroy and serves king Asgore. She is also incredibly hard to defeat and is not worth killing. In fact her heavy armor (And the fact that she is a fish) Makes it easy to just lure her somewhere hot and let her die of heat stroke. She is probably the reason that you should never go to the underworld alone... Undyne is fish-like humanoid monster, with blue scales and a long bright red ponytail. She has fins on the side of her head and a pair of protruding teeth. She wears an eyepatch on her left eye. She has yellow sclera; when she's lethally damaged however, it turns black.