The Egg King is a giant robot piloted by Eggman or Eggman Nega. The head has an Egg Mobile on it with a mouth guard. It also has spiky shoulders and big pillar-like hands with no fingers. Being a flying mech, it has no legs. It also has a triangular-shaped lower part with three fin-like blades around it. The character you are playing as determines the robot's color scheme:
Sonic: The upper torso, head, arms, and waist are white, the bottom torso, lines on the arms, hands, circle on the bottom torso is red, the spikes on the shoulders are dark blue, and the shoulders, arms and lines on various parts are black.
Blaze: The upper torso, head, arms, and waist are white, the bottom torso, lines on the arms, hands, circle on the bottom torso is pink, the spikes on the shoulders are light blue, and the shoulders, arms and lines on various parts are black.
Over the course of the battle with the Egg King, this boss will make use of the following attacks:
- Hand slam: The Egg King's main attack. It will slam both hands on the platform one at a time, creating orange rippling shockwaves that the player must jump over. It will move on to the arm attack move if the player hits one of the hands that remains on the platform after the attack finishes. This attack also gets faster and more unpredictable as the battle advances.
- Mega slam: The Egg King will reel back for a few seconds before smashing both hands on the platform, creating rippling orange shockwaves in both directions. This move will instantly defeat the playable character, regardless of Rings, if the player gets hit by the arms. However it only takes one hit to slam back. After the impact, the player can hit the arms to make the Egg King use the arm attack.
- Red laser: There are two variations of this attack. The first one is a continuous laser that the Egg King will fire at the playable character while pursuing them with it. The second one is a series of lasers that the Egg King will rapidly fire and will get faster and faster as they are fired. It is important to note that the lasers themselves do not harm the playable character; it is only the trail of explosions beneath them that hurts them.
- Purple laser: Similar to the red laser, this attack has two variations which are telegraphed when the Egg King pounds its fists together. The first one features a metallic box that the Egg King ejects above the player. This box will then create purple lasers that cage in the playable character. It randomly moves left and right of its own accord, and the player has to stay inside the boundary of the lasers to avoid taking damage. The second variation is much more tricky to avoid, as multiple purple lasers are ejected and spawn at random one after another. The player will get hurt if they do not stay inside the boundary of any of these lasers. As such, this is an incredibly difficult attack to avoid.
- Arm attack: The Egg King will use this attack when his arms were hit in one of the aforementioned arm attacks though it will also use this attack from one of the remaining attacks if the player avoids taking damage from them. The Egg King will move to the right end of the platform where it will then bash one of its hands on the end of the platform, creating green rippling shockwaves that travel to the left which can be avoided by jumping over them. The shockwaves will become more difficult to avoid as the battle advances; the Egg King bashes more frequently and hence generate more shockwaves which also travel faster. In this case, the player should use the Jump Dash or Burst Hover to avoid a couple of shockwaves in one jump. On normal difficulty, the Egg King may try to throw off the player's rhythm by bashing at inconsistent behaviors; it can bash quickly to generate a fast-moving shockwave or bash slowly to generate a slow-moving shockwave. If the player is standing at the very right end of the platform, it is possible for the player to be instantly defeated from the last bash, regardless of Rings. Once the bashing is done, the player must break an invisible shield by jumping onto its arm on the platform. Once it is disengaged, they must run along the arm to the cockpit, however, the Egg King will try and throw them off onto the main platform by shaking its arm. To stay on the arm, the player must hold down on . The player only gets three attempts to attack the Egg King's cockpit as after the third time, it will forcibly shake off the player even if they are holding down. During the later half of the fight on normal difficulty, purple laser boxes will be ejected from the cockpit while the player is running up the arm. While they can be destroyed by a Spin Jump or an Axel Jump, the boxes are best avoided as they may distract the player from trying to reach the cockpit or a safe place to crouch down.
When the Egg King has one hit point left, it will stop using all of its previous attacks and perform one final attack. During this move, it will attempt to destroy the playable character's platform by slamming into it three times. To overcome this attack, the player must jump into its head after its third time and finally defeat the Egg King. If the player takes too long to hit the Egg King however, it will crash through the platform and shatter it, causing the player to lose a life.
- The Egg King is one of the two robot bosses in Sonic Rush to not be based off of an animal, the first being Egg Libra.
- It is possible that this robot was inspiration to the Egg Dragoon from Sonic Unleashed as the battle took place on a falling platform that is broken as the battle goes on.
- This is one of two Eggman bosses that is named after a ruling figure (the other is the Egg Emperor from Sonic Heroes).
- This is the second boss fight in Blaze's story where Cream is absent of cheering on Blaze since Cream is kidnapped by Eggman prior to the boss fight.