The profiles of the characters straight from the Shadow The Hedgehog manual.

Main Characters

The black hedgehog who resembles Sonic. With his powerful body, he can easily rival Sonic's world class speed. Shadow was created as the Ultimate Life Form in a secret lab by Professor Gerald Robotnik. Everything else about Shadow's past is a mystery. After risking his life to save the planet with Sonic, he suffers from amnesia, having no memories of his past.
Doom's Eye is Black Doom's third eye. Doom's Eye accompanies Shadow throughout the game on Dark Missions and also helps locate Chaos Emeralds (nifty). In a way he's like Omochao, only less annoying.
Black Doom is the leader of the mysterious alien army that suddenly appeared in the sky bringing darkness and destruction to the world. As the leader he is in total control of the Black Arms. Who is he? Where did he and the alien army come from? And more to the point, how do they know our beloved black hedgehog? All questions will be answered once Shadow discovers his true identity.