The monster known for its dual nature as both man and beast in Greek mythology is the Minotaur. Born from the union of Pasiphae and a sacred bull, the Minotaur resides in the labyrinth of Crete, symbolizing the struggle between civilization and primordial chaos. This beast represents the darker side of human nature that can emerge when societal norms are challenged or broken. The hero Theseus ultimately confronts and defeats the Minotaur, signifying the triumph of reason and order over savagery.