Crotheon is a Vex Minotaur. His role is to protect Vex forces as they amass in the Black Garden to invade the Moon. He is destroyed by Guardian forces when they launched an attack to counter Vex encroachment on the Moon.
At times, Crotheon will become impervious to all damage due to shields. At this moment, the player must destroy specific Minotaurs that will drop a Vex cranium that can be used to take down his shield. Once his shield is down, the Guardian can damage him for about 20 seconds, and then his shield will recharge. Repeat the process until he is destroyed.