The Egg-Cerberus is a giant dog-like robot, although its different appearances in both Sonic and Shadow Episodes lead to speculation on whether or not there is one or two of them (since the one in Shadow's battle seems rusted.)
Powers and abilities
The Egg Cerberus is very fast for its size, capable of running at speeds nearing Sonic's. It can jump very high, and can impact the ground with enough force to create shockwaves over a wide area.
After Sonic and Tails were able to find and rescue Princess Elise who was kidnapped by Dr. Eggman, the doctor showed up and fought the heroes by unleashing the Egg-Cerberus upon them.
The battle occurs within a large round arena, in which there is a lot of room for the player to avoid the majority of the Egg-Ceberus' attacks. The Egg-Ceberus will primarily charge around the arena, but will eventually slow down to a complete stop between intervals, leaving itself vulnerable. To attack the Egg-Ceberus, the player must jump onto its tail (although the player can perform the Homing Attack towards it since the tail functions as a Grind Rail) which they will grind along to reach the antenna on its head.
Here, the Egg-Ceberus will begin charging again, but this time the player is able to control it. To damage it, the player will need to steer it so that it smashes itself against the arena wall. However if the player assumed control of the Egg-Ceberus while it is already too close to the wall, it will not be damaged if the player simply steers towards the wall as the Egg-Ceberus will simply run along the circumference of the wall. Instead, the player should aim for a wall on the other end of the arena. If the Egg-Ceberus is charging into a wall while its remaining health is less than half of its max health gauge, it will turn around and shake the player off, so the player must use the Homing Attack to grab back onto the antenna. If the player takes too long to damage the Egg-Ceberus, it will eventually shake them of its antenna. Each hit takes a quarter of its max health gauge but if the player steers the Egg-Ceberus against a statue it will take half of its max health gauge.
Once the Egg-Ceberus' remaining health reaches to half of its max health gauge, the Egg-Cerberus adds in another attack; it will leap out of the arena onto a circular ledge (the camera will pan from a lower angle so the player can see this). After a few moments, it will jump high into the air and emit a shockwave upon landing. To avoid this, the player should note the shadow of the Egg-Ceberus as an indicator of where it will land, and that the shockwave can be avoided by simply jumping.
The battle is nearly identical to Sonic's version, with the only difference being that there are no special objects on the arena wall for the Egg-Ceberus to smash itself into for double the damage. Enemies such as the Egg Gunner are also present.
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.
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".
↑Sonic Team, Sonic Team USA (14 November 2006) Sonic the Hedgehog. Xbox 360 Area/Level: Egg Cerberus (Dusty Desert). "Sonic the Hedgehog: This is your pet, huh? Okay, Eggman, I'll play with him."
↑Sonic Team, Sonic Team USA (14 November 2006) Sonic the Hedgehog. Xbox 360 Area/Level: Egg Cerberus (White Acropolis). "Shadow the Hedgehog: The Doctor's Guard Dog... Still, I need to get though here."