Chaos Emeralds

"With the fate of the Chaos Emeralds at stake, it’s up to Sonic, Tails,  Mighty, and  Ray to unite against a superpowered Metal Sonic."

- A part of the description in Metal Mayhem.

The Chaos Emeralds are seven very important jewels connected to the Master Emerald that grant their wielder incredible powerful states. They can power machines, people, warp through time and space and many more things. These spectacular abilities they give are no wonder why the evil Doctor Robotnik wants them so dearly.

Sonic Returns
When Sonic gets captured by Dr. Eggman and gets set next to a ticking time bomb, Sonic pretends to give him the green Chaos Emerald. He makes Robotnik turn around and get trapped in his own trick. Sonic leaves with the Flickies' help, after feeling guilt by Robotnik's face of sorrow. He discovers Robotnik has some kind of device which scans for emeralds. It reads that Sonic has one, Robotnik has four and an unidentified entity has two. Sonic angrily punches the bomb, making it tick down faster. He runs off.

Sonic And Tails
Sonic hands over the device to Tails. The device locates that a red emerald is somewhere near them. A rumble quakes the ground and showcases smoke coming from out the forests. It's Robotnik drilling in the ground, trying to find the emerald. Sonic and Tails then beat him up. After that, they cling both red and green emeralds, laughing in the end.

Mighty And Ray
Ray is trying to search for his friend Mighty, but gets attacked by Metal Sonic. Mighty comes into play, but Ray gets choked by Metal. Metal Sonic demands to give him the white emerald. Mighty, with a sigh, gives the emerald, but angrily throws a rock at him. Mighty and Ray follow Metal Sonic to Robotnik's lab, so they can defeat Metal Sonic and Dr. Robotnik. But they also see Sonic, Tails and Knuckles headed that way as well. Although Knuckles is only running for the Master Emerald being taken.

Metal Mayhem
Sonic and Tails arrive in the lab, but see nothing. Until Metal crashes onto the ground, freezing the two in a freeze box. He releases the two together with their chaos emeralds, he snatches them. Robotnik then appears, tossing the Chaos Emeralds in each hand whilst manically laughing. Metal absorbs all of the emeralds' power.

Everyone tries to fight Metal, and Sonic and Tails hatch a plan. Sonic runs around Metal, confusing him whilst Tails freezes him. The box drops and releases the Chaos Emeralds.