Shadow is an artificial created life form in the design of a male, anthropomorphic hedgehog. He resembles Sonic in many ways, such as how his hover skates propel him at extreme speeds to rival those of Sonic; but he distinguishes himself with greater use of his signature ability to use Chaos Control with Chaos Emeralds. He is Sonic's rival and is the anti thesis of Sonic himself in all aspects of Shadow's life. The rings attached to his wrists suppress his power.

Shadow vowed to keep his promise to Maria, a girl he befriended on the Space Colony Ark, to give humanity a chance to be happy. He once blamed humanity for Maria's death, but came to realize that Maria wanted the people on Earth to live happy lives.