Shadow the Hedgehog is a fictional character created by Takashi Iizuka, who appeared in the Sonic the Hedgehog series made for the Sega Console. He debuted as a video game character in the Sonic Adventure 2, from then on, he has appeared in many other games trying to figure out who he is and what should he do with his life. When Sonic Adventure 2 was in development, Shadow was originally named Terios the Hedgehog, the term terios means "reflection of". His name was changed to Shadow before Sonic Adventure 2 was released.
Shadow is one of Sonic's main rivals, he can do everything that Sonic can do and at some instances perhaps even more. He's a neutral character as McBoo.