The Chaos Emeralds are seven fictional gems from the Sonic the Hedgehog series. The Chaos Emeralds have mystical properites and abilities, and the holder of them all can use them for a large variety of things, such as transforming into a powerful "super form" and raising the dead. Each emerald is composed of positive and negative charged materials which make them an everlasting source of energy and allow them to float in the air. All player characters that are capable of transforming only use the positive charged part of the Emeralds to do so, which is demonstrated by Sonic at the end of Sonic Adventure (except possibly Shadow, who had been shown using positive and negative energy in Shadow the Hedgehog and Sonic Adventure 2 respectively). Sonic the Hedgehog is the first character seen with the ability to merge with the Chaos Emeralds when transforming into Super Sonic, shown in Sonic Unleashed and Super Smash Bros. Brawl, and Shadow was the second, seen in SEGA Superstars Tennis. After a super form is reached, the Emeralds discharge and send themselves across the world (or to special stages), and as such characters often collect them throughought the games. While they were more like "bonus" items in the early games of the series, the Chaos Emeralds became nessicary plot devices in Sonic Adventure, and that trend has continued throughout the later 3D games.