Angel Island is a floating landmass above Sonic's world, kept afloat by the mystical Master Emerald. Both the island and its source of flight is often guarded by the islands sole resident, Knuckles the Echidna.
Knuckles the Echidna has guarded Angel Island for a long time, however, there were times where Knuckles had to leave his post and leave it unguarded for one reason or another. Most recently, during the war between the Eggman Empire and the Resistance, Knuckles left the Island in order to become the commander of the Resistance. (StH: #3)
The Battle for Angel Island
Eventually, Neo Metal Sonic discovered that, with Knuckles on the surface, the island and the Master Emerald was unguarded. He took note that the Master Emerald would help accelerate his plans. (StH: #3)
Ready to proceed with his plans, Neo Metal Sonic invaded Angel Island's airspace using the Egg Fleet and its forces. With no resistance from the unguarded island, Neo Metal Sonic managed to establish his forces there and put its airspace into lockdown with his Egg Fleet. He then secured the Master Emerald for himself inside a fortification he built around the Master Emerald's shrine. (StH: #7, #8)
After taking over Angel Island, Neo Metal Sonic converted the floating island into a gigantic flying fortress. During a thunderstorm however, Sonic the Hedgehog and his allies arrived in a Battleship to liberate the island. Although the Egg Fleet shot the battleship down on its way to Angel Island, all its passengers evacuated in time and began their appointed missions around Angel Island. Team one consisted of Blaze the Cat in her Burning Blaze transformation, and team two consisted of Amy Rose, the Chaotix, Tails, Silver the Hedgehog, Tangle the Lemur, Rouge the Bat, and Whisper the Wolf. The two teams began working on breaking the Egg Fleet's control over Angel Island while team three, which consisted of Sonic and Knuckles, confronted Neo Metal Sonic in order to secure the Master Emerald and rob the Egg Fleet of its commander. Shadow the Hedgehog, who was originally assigned to team two, left the group to do his own thing. When Sonic and Knuckles encountered Neo Metal Sonic, Neo used the Master Emerald to transform into Super Neo Metal Sonic during their confrontation. (StH: #9)
While Sonic and Knuckles fought Super Neo Metal Sonic, team one and team two focused on removing the two wing units that were attached to Angel Island's shoreline. However, the former team was unable to make much progress, so Tails sought a smarter approach. Meanwhile, Burning Blaze managed to destroy the island's left wing unit, losing her transformation in the process and landing on on the island below. Tails and Silver winded up taking control of an Egg Fleet battleship, which they used to destroy the island's last wing unit. The Resistance and their allies subsequently regrouped onboard the battleship that Tails had hijacked. At the same time, Shadow came to Sonic and Knuckles' rescue and forced Super Neo Metal Sonic to change back into Neo Metal Sonic. However, Neo Metal Sonic managed to successfully copy Shadow's bio-data, which he used in conjunction with Sonic's bio-data (which he already had) and the Master Emerald to transform into an even bigger threat: Master Overlord. This metal monstrosity scooped up the Master Emerald, effectively cutting Angel Island off from its power, which meant that Angel Island was on the verge of falling into the ocean. (StH: #10)
As Angel Island began to fall, Blaze flew away from the island and joined her team on their battleship while Sonic, Knuckles, and Shadow got taken off the island by Master Overlord. Fortunately, the heroes defeated Master Overlord and Knuckles got the Master Emerald back to its shrine on Angel Island, allowing the island to resume flight just before it fell into the ocean. Afterward, the heroes as well as a now offline Metal Sonic, landed on Angel Island. (StH: #11)
Despite the massive battle that had just occurred, Angel Island appeared intact. In order to remain on Angel Island and guard the Master Emerald however, Knuckles renounced his duty as the Resistance's commander by disbanding the organization, concluding that it had served its purpose. The rest of the new arrivals on Angel Island would then gather onboard a damaged Egg Fleet battleship. After repairing the battleship, Tails got everyone onboard off of Angel Island. (StH: #12)
- Angel Island first appeared in Sonic the Hedgehog 3. As the home of Knuckles, and the location of the important artifact, the Master Emerald, it has since become a reoccurring location for the series.