Eggrobo (Sonic Lost World)

"I'm sick of you getting in the way EVERY SINGLE TIME!"

- Doctor Eggman

The Lava Mountain final boss is the final boss of both Lava Mountain and Sonic Lost World. Dr. Eggman pilots a huge mech that harnesses the energy of Sonic the Hedgehog's world from Eggman's Extractor.

History
The machine was constructed by Dr. Eggman in the period before the Deadly Six rebelled against him in Sonic Lost World, and was designed to be powered by the energy harvested from the Extractor. Before Eggman could deploy this mech, however, he was driven off from his operations by the Deadly Six when they broke free from Eggman's control due to Sonic's actions.

To get to his ultimate weapon again and as well stop the Deadly Six from using the Extractor to destroy the Earth, Eggman teamed up with Sonic and Tails. When Eggman and Sonic got to Lava Mountain, however, Eggman faked his own death by pretending to fall into a lava pit when he seemingly sacrificed himself to save Sonic, so he could get to the Extractor and his ultimate weapon without anyone knowing. While Sonic then took care of the Deadly Six, Eggman shut down the Extractor and used the energy it had harvested to super-charge his ultimate weapon.

When Sonic and Tails finally made it to the Extractor to shut it down, they discovered that was shut off prior to their arrival, before Eggman ambushed them in his ultimate weapon. After Eggman had explained how he survived when he saved Sonic, the doctor revealed his plans to conquer whatever that was left of the world from the Extractor's effects with the same energies it had harvested. However, Sonic did not intent to let Eggman go through with his plan and engaged Eggman in his ultimate weapon in a fight. In the end, the ultimate weapon was no match for Sonic, and was utterly destroyed by Sonic's hands.

Wii U Version
The beginning of the battle takes place in a narrow, straightforward platform aisle that Sonic the Hedgehog runs on after being fired from a cannon. The final boss will launch its hand to the player, and will shoot out a laser that will stay in the same spot for a few seconds. After that, the final boss will launch three craters to the player and try to make the player lose their rings. Once this has been done, the player has the opportunity to hit the final boss via Homing Attack on the mech's model parts until they reach to the mech's face. Once hit, the mech will fall on the ground and roll until it manages to pick itself up again. Sonic has a chance to homing attack the mech while its rolling to deal additional damage.

3DS Version
The battle begins with Sonic already running after Eggman's mech. During the battle, Eggman uses powers of the Laser, Burst, Drill, Lightning, Asteroid, and Quake. Between every attack, the power of the mech will be shown and will increase as the mech loses health. In Easy mode, it will start from 1000, then go up to 8000, then finally 10000. In Hard Mode, it will start from 1000, but temporarily go up to 5000 for 1 attack, then go down to 1000, then 8000, then finally, 10000. Finally as the boss of Lava Mountain Extra, it will start at 5000, then 8000, 10000, and will go past it's limits as it reaches a power of 100000. When the mech is at it's final power level, when Sonic has a chance to free 2 Wisps and 1 extra Wisp by landing an extra hit on it. Do this twice, and Sonic will have freed 6 Wisps, each Wisp granting Sonic some sort of strange power. After 6 Wisps have been freed, Sonic will charge at Eggman and use a super-charged homing attack powered by energy collected from the mech, forcing the player to rapidly press the B button in order for Sonic to overwhelm the mech's defences and blow it up.

Trivia

 * The machine has many similarities to various creations made by Dr. Eggman:
 * It has a similar design to the Death Egg Robot from Sonic the Hedgehog 2 and Sonic Generations. The cape is also similar to the cape worn by Metal Robotnik from Sonic the Hedgehog: The Movie. The color scheme is also similar to Egg Dragoon from Sonic Unleashed and Sonic Generations.
 * The battle between the ultimate weapon and Sonic has some similarities to the Egg Nega Wisp fight from the Wii version of Sonic Colors.
 * Also, much like the battle with the Egg Nega Wisp, when Eggman is defeated, he is ejected from his mech and sent soaring into the distance, becoming a Eggman shaped firework when he's out of sight.
 * Much like the Time Eater from Sonic Generations, the 3DS version uses more attacks than the console version. Also, like the Time Eater, both versions differ slightly in appearance (the cape on the 3DS version appears much smaller).