Shine the light on the Egg Phantom to reveal what's inside!
— Loading screen, Sonic Rivals 2
As the name states, the Egg Phantom is a giant, robotic phantom with the Egg Mobile as its head. Most of its body is light-blue and has a pumpkin-like face. It only has a head, giving it a ghost-like model.
There are several benches in the room which have light switches on them. As the Egg Phantom flies around the room, players must jump on the switches to lure the boss to the light. If the Egg Phantom touches a light, it will become transparent, revealing Eggman Nega's hovercraft. This is the player's chance to attack. The Egg Phantom's only offensive attack is touching the player while Eggman Nega is concealed.
Six hits from the player marks the end of the fight and victory for the player.