WaterHag

WaterHag is a boss from Final Fantasy Legend III - resembling a large fish-man hybrid (akin to a murloc or Deep One) this fearsome creature stands as an opponent to the story's time-travelling protagonists and fights them in an effort to stop them from installing the Past Unit into the Talon (a mystic-vessel) and thus prevent them from interfering with its masters' plans: however the monster was not powerful enough to defeat the heroes and was presumably slain.