The Doomsday Zone

After his defeat, Dr. Robotnik lands on Angel Island, where he finds an energy source even more powerful than the Chaos Emeralds, namely the Master Emerald. However, it was protected by the powerful guardian Knuckles the Echidna. Despite his power, Knuckles is rather gullible, so Robotnik convinces the echidna that Sonic and Tails are trying to steal the Master Emerald, thus turning Knuckles against the heroes. Soon, Sonic and Tails arrive on Angel Island and are immediately attacked by Knuckles, who takes the Chaos Emeralds from the heroes and hides them around the island. Sonic and Tails pursue Knuckles and Robotnik, recovering the Chaos Emeralds along the way.

After destroying the Launch Base, the heroes find a portal to the Master Emerald, which they use to enhance the Chaos Emeralds to Super Emeralds. Using their power, Sonic uses the Hyper Sonic form and Tails uses the Super Tails form. Together the heroes defeat Knuckles, but Robotnik takes advantage of this to steal the Master Emerald. Realizing his mistake, Knuckles helps the heroes pursue the doctor. Sonic and Tails, in the process defeating another iteration of Metal Sonic – Neo Metal Sonic, make their way to the Death Egg rebuilt with the help of the Master Emerald. Facing off in the final battle, Sonic and Tails defeat Great Eggman Robo, but even then Robotnik doesn’t give up and tries to escape in his Final Weapon.

Sonic, using his Hyper Sonic form, catches up with the villain and fights his Final Weapon in open space, in a place which is keeping a symbolic name – The Doomsday Zone. First, Hyper Sonic chases the Final Weapon through an asteroid field while the Final Weapon fires off missiles. Afterwards, Hyper Sonic forces the Final Weapon to fire missiles at close range, then redirects the missiles into the machine itself, thereby destroying it. However, even after the destruction of the Final Weapon, Robotnik escapes with the Master Emerald in his Death Egg Bot which was kept in Final Weapon, but Hyper Sonic catches up with the villain and finally retrieves the Master Emerald, finally defeating Robotnik. After the battle, Hyper Sonic returns the Master Emerald to Knuckles and together with Tails on Tornado, the duo leaves the Angel Island.