Undyne is a piscine, anthropomorphic monster. She has blue scales and a long red ponytail. She has red and blue fins on the sides of her head, and a pair of sharp, yellow, protruding teeth. She wears a red eyeshadow and has an eyepatch over her left eye. She also wears a black tank top and blue jeans, but debuts in armor varying in light and dark shades of gray. She is capable of conjuring spears at a moment's notice. She is heavily patriotic towards the underground.