MINOTAURS

According to Greek mythology, Minos, the king of Crete, had a white bull which was meant to be sacrificed to Poseidon, but Minos felt that it was too beautiful to kill. Poseidon punished him by cursing his wife Pasiphae to fall in love with the bull. After some events which I won't go into here, Pasiphae gave birth to the Minotaur - a monster part man, part bull. It's usually depicted as a man with a bull's head, although Thomas Bulfinches famous book on mythology, The Age of Fable, describes the creature as a bull with a man's head. I don't know if this is from an alternate version of the legend or was a slip-up by Bulfinch.
The Minotaur ate humans, so the craftsman Daedelus built a labyrinth to contain it, and Minos ordered that each year, seven youths and seven maidens from Athens (a town Minos hated after his son was killed by a bull there) were to be sent into the labyrinth to feed the Minotaur.
The hero Theseus decided to kill the Minotaur, and set sail for Crete. Upon arriving, he met Mino's daughter, who gave him some thread with which to mark his path through the maze. After killing the Minotaur (with either a sword or his bare hands, depending on the version of the story), Theseus followed the thread and escaped the labyrinth.