The Asteroid Coaster sub-boss is actually a giant robotic eye with three shields. The eye is red, while the rest of the parts is light and dark gray and with some cyan lines. The shields are red and orange, which on the screen looks like the shields are on fire. The gravitational field around it is purple.
At the end of Asteroid Coaster Act 6, Sonic falls into a circular arena, where the sub-boss awaits. The sub-boss has no method of directly attacking Sonic, but instead damages Sonic using its defenses, generating three electrical shields circling around itself. It also forms a zero-gravity field around itself, into which Sonic must jump. Once caught in the zero-gravity field, Sonic will rotate around the sub-boss, and a Homing Attack target will appear, allowing Sonic to attack his enemy. However, Sonic must time his Homing Attack carefully, because if he mistimes it, he will hit one of the sub-boss' three shields and take damage. Once it takes damage, this enemy's eye and the zero-gravity field will disappear and the process repeats. Three hits are required to destroy this enemy. Once defeated, the flaming sub-boss will fall and explode, destroying the trapdoor at the bottom of the arena and allowing Sonic to skydive to the Goal Ring.
- This is the only sub-boss of the game, not counting the Big Chaser.
- This enemy is fought in a 2D circular arena, similar to the Rotatatron and Refreshinator battles.