|Kind of Item||Gem|
|First Appearance||Sonic the Hedgehog (1991)|
|Invincibility and increased speed|
The Chaos Emeralds are powerful gems in the Sonic series. It is said that they hold mystical energy that can grant extraordinary powers to anyone who uses them, as long as they gather all seven. Their energy also maintains balance on Earth in a sense; they hold the continents together and prevent islands from sinking to the bottom of the ocean.
In ancient times, there was a large tribe of echidnas who guarded the emeralds and their main source of stability, the Master Emerald. Most of them were wiped out by the beast known as Chaos, and eventually, it got to the point where Tikal (the princess of the tribe) had to seal herself in the Master Emerald with him. The seven gems were named the Chaos Emeralds after Chaos, and they would forever be known as a source of brilliant power and energy.
The powers the Chaos Emeralds can grant a living being varies between games. Usually, they give the user invincibility and increased power, speed, etc., but they can also be used to alter the space-time continuum (as seen when Shadow uses Chaos Control) or power machines like the Death Egg and Metal Sonic.
Sonic Speedball series
The Chaos Emeralds were planned to be in the entire Nightwolf series, but only appeared in Nightwolf the Game. By then, Omegaverse Corp. thought to include them in one more game, Hyper Nightwolf, but it didn't happen.
They appear in the Micool series that can make Mick Cool transform into Super Mick Cool and can Micool super as well. But if Micool is enraged or depressed when using the emeralds he will transform into Dark Micool.
Chaos Emeralds make an appearance in Sonic Heroes 2 as power-ups for Chaos Emerl. They are present in Aqua Lake Zone, Great Turquoise Zone, Sandopolis, Casinopolis, Scrap Brain Zone, Station Square and Sleeping Egg Zone.
The Chaos Emeralds (and the Master Emerald to a lesser extent) play a huge role in the Spursverse movies and video games. They were introduced to the franchise in Super Mario Silver Spurs: The Crossover Vacation, where Mephiles the Dark and his army went after them so he could destroy the universe and create his own in its place.
In Dimensional Duos, it was revealed that there was an eighth Chaos Emerald -- the black Eclipse Emerald. Mephiles offered this emerald to Nergal Jr. if he helped him destroy the Multiversal Guardians once and for all. The latter eventually betrayed him, though, and stole the Eclipse Emerald to fuse with some of the multiverse's worst monsters and try to take over reality.
After the universe was rebooted, the events of Multiversal Silver Spurs depicted a new batch of Chaos Emeralds, this time excluding the black emerald from the old timeline. Said timeline was restored in Continuum Renegades, but it was fused with the new one, causing a disturbance in the cosmic balance. In Silver Spurs Omicron: Echoes of Disaster, it was shown that the old timeline's Chaos Emeralds, including the Eclipse Emerald and the Master Emerald, have been carried over to the fused universe. It is currently unknown whether or not this caused the cosmic anomalies in the current state of the Spursverse.