The Chaos Emeralds (カオスエメラルド Kaosu Emerarudo), also known as the miracle gems or gems of miracles, are objects that appear in the Sonic the Hedgehog series. They are seven ancient emeralds and secret stones tied to the Master Emerald that possess unlimited power. Those that hold them can use them to cause miracles and other feats, such as warping time and space, powering machines, and initiating super transformations. Anyone who combines all seven Chaos Emeralds can control unimaginable power. Even when not including their mystical powers, the Chaos Emeralds' monetary value and beauty make them prime targets of treasure hunters who seek to make a mint. The Chaos Emeralds have observed numerous joys and sorrows since ancient times, being the center of countless world-threatening conflicts and targeted by multiple factions on earth and beyond, who seek them for their near-limitless 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 the Master Robot incident, they have become necessary plot devices, and that trend has continued throughout most later games.