"The Egg Cerberus is one of Dr. Eggman’s most terrible creations a hulking metal monster capable of trampling Sonic the Hedgehog beneath its thunderous gallop. The clockwork monster thunders around the crumbling arena, smashing columns and causing mayhem. To survive this encounter, Sonic must somehow ﬁnd a way to tame the savage metal beast, even if it’s for only a moment. Egg Cerberus’s weak point is a neon pole on its head. Sonic must scale the robotic canine and grab the pole, then steer the menace. The giant stone walls that surround the arena are the perfect thing to slow down this runaway terror."
It is a giant dog-like robot, although its appearances in both Sonic and Shadow's stories lead to speculation on whether or not there is one or two of them. (Since the one in Shadow's battle seems rusted.)
The boss' defeat requires the player to grind on their headrest, hold on to its head antennae, and lead them into a wall. This gets harder after time, as the Egg-Cerberus will refuse to obey orders. In Sonic story the player can do much damage to the Egg Cerberus if the player lead him to the statue causing to deplete half of Egg Cerberus Health Gauge.
The Egg-Cerberus is named after a dog in Greek mythology, Cerberus, who was a three-headed, fire-breathing, demonic dog who guarded the entrance to Hades' Underworld. However, the Egg-Cerberus has only one head, unlike the Cerberus in mythology.
The Egg-Cerberus bears a slight resemblance to Metal Hound, another Eggman robot made to resemble a dog.
During Sonic's battle, the Egg-Cerberus is referred to as Dr. Eggman's "pet" and in during Shadow's battle, it is referred to as his "guard dog".