Asterius, also known as the Minotaur, is a bull-headed demi-human who was recruited by Hades to help prevent Zagreus's escape. He fights by himself as a mid-boss of Elysium, or alongside Theseus as a final boss.
In life, Asterius was locked in a labyrinth by his father, King Minos, only to eventually be slain by Theseus. In death, the two are apparently comrades.
Asterius cannot be given Ambrosia.
||'...In life, the wretched abomination known as the Minotaur was feared across the coast of Greece; those cast into the Labyrinth in which he, himself, was trapped had no hope of escape. That was until the young hero Theseus entered the Labyrinth voluntarily, and slew him in what was, by most accounts, a spectacular battle. A famous tale -- but what happened when they reunited in death needs to be told, as well. Here, they say Theseus again discovered the Minotaur, whose soul had lingered restlessly at the edge of the Underworld, and Theseus took pity on him. Though, I think there is more to it than that.I think Theseus saw in the bull-man Asterius his greatest rival. Thus he offered Asterius a seat of honor in Elysium alongside him; a just result, for their fame and glory are intertwined.'
For additional information on Minotaur that does not pertain to Hades, see Wikipedia's article: Minotaur