Master Emerald

The Master Emerald is a large diamond-cut jewel which controls the ability of the Chaos Emeralds to absorb Chaos energy from the Chaos Force, able to increase their intake or decrease it to zero.

The Master Emerald resides in the Altar of the Emeralds on Angel Island, where it channels energy from the Altar to keep the Island afloat. The Master Emerald is also home to the spirits of Tikal and Chaos.

History
In the mid-20th century during his study of the Echidna civilisation, human scientist Gerald Robotnik studied the Master Emerald as part of the development of the Space Colony ARK.