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.