

Shadow, the Black Blur, is the spitting image of Sonic and shares his agility and speed. However, unlike Sonic, his body is black - and, as the most violent and merciless character in the series at times, he is, personality-wise, Sonic's polar opposite. Shadow has found himself in cahoots with the evil Dr. Eggman in the past, doing all he can to secure Sonic's downfall - though, of course, he never succeeds. But Shadow's motivation is never really that simple; he spends as much time grappling with his own inner demons as he does with Sonic.
Shadow made his dark debut in the SEGA Dreamcast game Sonic Adventure 2, where it is revealed he was created as the 'ultimate life form' by Professor Gerald Robotnik. However, most of his past was a mystery to players until Shadow the Hedgehog, where it was discovered that Dr. Eggman's grandfather created him using Black Doom's DNA. (Which technically makes Black Doom Shadow's father!)
When Shadow first appears, he is suffering from amnesia and doesn't know whether he has been designed for good or for evil - although he tends to opt for whatever path suits his goals at the time. Shadow's varying actions are a result of his continuing grief for the loss of his friend Maria, Gerald Robotnik's kind and gentle granddaughter. He witnessed her death when she sacrificed herself aboard the ARK, allowing him to escape to Earth from GUN forces attacking the space station. When she died, she made him promise to save the world... although from who or what was not clear for some time.
Shadow's greatest assets are his Air Shoes (also sometimes referred to as Jet Shoes and Hover Skates). Their powerful jets enable Shadow to skate as fast as Sonic runs.

If the world chooses to become my enemy, I will fight like I always have!