Shadow the Hedgehog

Shadow the Hedgehog is one of the main protaginists of New Super Mario Bros. Z.Shadow is a black hedgehog, who resembles his rival, Sonic the Hedgehog. Shadow is known as the Ultimate Life Form and was created by Eggman's grandfather Gerald Robotnik. The United Federation funded the project and created with the help of Black Doom to cure Maria Robotnik of her illness. the military deemed the project to dangerous and Shadow was kept in stasis for 50 years, until Eggman freed him.

Pre Mecha Sonic Saga
Shadow was on Mobius as the Death Egg crashed down on the planet,destroying it due to Mecha Sonic being unleashed. Mecha Sonic then started an onslaught on the many citizens and animals of Mobius, including Shadow's friends Rouge the Bat and E-123 Omega. Seeing the dead bodies of his fallen comrades Shadow changed into an even colder person and thus wanted revenge on Mecha Sonic. As Sonic was being beaten around by Mecha Sonic, the robotic beast had all 7 Chaos Emeralds and began to undergo a transformation. however, Shadow showed up in time and used Chaos Control to send the Emeralds to another world ( The Mushroom Kingdom). mecha sonic didn't quit however, and used his own Chaos Control to transport himself to the Mushroom kingdom to reclaim the 7 Emerlads. Sonic and Shadow were then left in the ruined, burning planet of Mobius, but they went to the wreckage of the Death Egg, found two of Eggman's teleporter machines and teleported into the Mushroom Kingdom.