Shadow

He is an anthropomorphic hedgehog/Black Arms hybrid who resembles Sonic the Hedgehog in many ways[9] and serves as his arch-rival and occasional ally. Shadow was created as the "Ultimate Life Form" (究極生命体, Kyūkyoku Seimeitai?) by Gerald Robotnik by using the DNA of Black Doom and is the final result of Project Shadow. His purpose was to provide ways to develop a cure for incurable deadly illnesses, more specifically for Gerald's granddaughter Maria Robotnik, who he had a great bond with. However, he was eventually captured following his creation and put into stasis by G.U.N. when he was deemed as a threat to humanity.