Master Emerald (IDW)

The Master Emerald is an object that appears in the Sonic the Hedgehog comic series published by IDW Publishing. Guarded by Knuckles the Echidna, it is a massive green emerald and a mystical relic of immeasurable power that rests on Angel Island, where its power keeps the island afloat in the sky; without it, the island will fall down.

Past
For an unknown length of time, Knuckles the Echidna has guarded the Master Emerald from anything capable of posing a threat to it. Recently, though, he was required to leave it when Dr. Eggman conquered the majority of the world after capturing Sonic the Hedgehog.