The Labyrinth

And Asterion coddled the limp forms that rose from the refuse above. In time, they grew from weak animals into violent hunters. He found that their wild rage carried his own, and together they lived as one flame in the darkness. 

I imagine the Minotaur was a crippled and deformed giant. In between tributes to Crete, this creature must have eaten other things. Likely, living off of garbage tossed into the Labyrinth. Sometimes the soldiers threw rotting corpses into the fodder for a laugh. And sometimes the corpses weren't quite so.