Master Emerald

The Master Emerald (マスターエメラルド Masutā Emerarudo?) is an object that appears in the Sonic the Hedgehog series. It is a massive green emerald and a mystical relic of immeasurable power from the forgotten past. Created by the gods, the Master Emerald acts as a counter to the Chaos Emeralds. The one who controls the Master Emerald can nullify and control the Chaos Emeralds, making the Master Emerald a very valuable gem.

The Master Emerald rests on Angel Island where its power keeps the island afloat in the sky; without it, the island will fall down. Over the last four millennia, the Master Emerald has been guarded by the surviving echidnas of the Knuckles Clan who has kept the gem safe from those seeking it for their own gain. In the present day, its current guardian is Knuckles the Echidna.

Appearances in Idea Wiki

 * The Master Emerald appears in the continuity of Marvel's Spider-Man: Webbed Champion.
 * It is seen in the crossover episode "Legendary Universes, Part 3: Unlimited Speed", when Spider-Man and his team visit Mobius under Sonic the Hedgehog's guidance.
 * Also appearing in the show's Disney+ sequel miniseries Marvel's All-Star Multiverse, the Master Emerald is stated to be one of the "doorways" to unlock the Multiverse Star, with the Chaos Emeralds serving as the keys.