Power Gem

Power Gems (also called Power Stones) are an energized mineral similar to Chaos Emeralds found on Mobius. Properties of Power Gems include increased all around power, the ability to increase the size of objects, and the ability to upgrade or power machines. (KCX)

Due to an unknown fluke, one temporarily transported Sonic the Hedgehog, Mighty the Armadillo and Ray the Flying Squirrel into an alternate zone; it apparently affected the flow of time as Sonic and Mighty reappeared almost instantly despite having experienced a longer time within the zone itself, and Ray, who was later found trapped with the gem, experienced what seemed like mere hours to him over the course of nearly a decade. (KtE: #26, #27, #28)

Years later, Dr. Ivo Robotnik used a Power Gem to boost the power of the original Metal Sonic, which caused him to transform into an unnamed giant red robot. However, Knuckles' also used the gem's power to enlarge himself, and defeated the robot. Despite this, Metal Sonic survived and repaired himself. He later located and fought Sonic, defeating him with ease due to having the power gem embedded in his chest. However, Metal Sonic sacrificed his life to save both Sonic and Tails after being convinced to surpass his programming, and he along with his power gem were destroyed by lava flow from Mount Mobius. (StH: #86, #87, KCX)