Chaos Emeralds

The Chaos Emeralds (カオスエメラルド Kaosu Emerarudo?) are reoccurring objects that appear in the Sonic the Hedgehog series. They are seven ancient emeralds and mystical relics tied to the Master Emerald, with powerful properties and abilities. Those that hold the Chaos Emeralds can use their powers for a variety of things, such as initiating a super transformation, powering machines, and warping time and space. Anyone who combines all seven Chaos Emeralds can command ultimate power.

Throughout history, the Chaos Emeralds have been the center of countless world-threatening conflicts and have been targeted by multiple factions on both earth and beyond, who seek them for their immeasurable powers. In the hands of villains they have been used for doomsday weapons and schemes for world domination, and in the hands of heroes they have been used to save the world. Over time, the Emeralds have been gathered multiple times, though they tend to scatter themselves after each usage and reset the hunt for them.

In the early games of the series, the Chaos Emeralds were more like "bonus" items, but since Sonic Adventure, they have become necessary plot devices, and that trend has continued throughout the later games.