A mysterious labyrinth, with a loud battle cry within. Picture from Wallup.com
Minotaur
Mostly based on myth
The Minotaur myth originated in ancient Greece. It translates to "Bull of Minos". The myth took place on the Island of Crete. The city of minos had a massive maze underneath it built by the scribes Daedalus and Icarus. Within the lost structure lived a large monster with a bull's head and hooves, and a muscled humanoid body, wielding a greataxe the size of a person. Its roars were so loud it could create earthquakes above in the city. It was eventually killed by the Athenian warrior Theseus. In d&d, minotaurs are the spawn of the demon lord of beasts, Baphomet. They have the same physical appearance, but lack the earthquake like roar.
In mythology
Theseus and the minotaur, approximately made in 500 B.C.E