Shadow

(also known as The Ultimate Lifeform, Project, Faker, Android, Traitor or Terios) is mobian hedgehog - black arms hybrid

Biography
Fifty years before the events of Sonic Adventure 2, a top-secret project known as "Project " had begun on the Space Colony ARK. Led by Professor Gerald Robotnik, it was a government-sanctioned initiative to create "The Ultimate Lifeform," an immortal being that could be used for the benefit of the nation, likely in a militaristic fashion. While Gerald had initial misgivings to the purpose of the research he was assigned to, he realized that his results might be able to save his granddaughter, Maria. Suffering from the incurable disease Neuro-Immune Deficiency Syndrome, Maria only had a short time left to live, and Gerald was willing to do whatever it took to save her life. Going against his worries of stepping into territory man had no business playing with, the professor immediately began work, hoping that he could apply any newly-gained knowledge to find a cure to N.I.D.S.

Dreamcast Era

 * Sonic Adventure 2
 * Sonic Heroes
 * the Hedgehog

Rivals series

 * Sonic Rivals


 * Sonic Rivals 2

Riders series

 * Sonic Riders


 * Sonic Free Riders


 * Sonic Riders: Zero Gravity

Storybook series

 * Sonic and the Secret Rings


 * Sonic and the Black Knight

Mario & Sonic series

 * Mario & Sonic at the Olympic Games


 * Mario & Sonic at the Olympic Winter Games


 * Mario & Sonic at the London 2012 Olympic Games


 * Mario & Sonic at the Sochi 2014 Olympic Winter Games


 * Mario & Sonic at the Rio 2016 Olympic Games

Super Smash Bros. series

 * Super Smash Bros. Brawl


 * Super Smash Bros. for Nintendo 3DS and Wii U

Sega Superstars series

 * Sega Superstars Tennis


 * Sonic & Sega All-Stars Racing


 * Sonic & All-Stars Racing Transformed

Modern Era

 * Sonic Battle


 * Sonic the Hedgehog (2006)


 * Sonic Chronicles: The Dark Brotherhood


 * Sonic Colors


 * Sonic Generations