Shadow was created by Gerald Robotnik, the grandfather of Dr. Eggman, as his second attempt to create the ultimate life form. His original purpose was to use for research on terminal diseases, and possible cures for them, as Gerald's granddaughter, Maria Robotnik, was suffering from one. However, he was considered by the forces of G.U.N. to be a worldwide threat, and their home, the Space Colony ARK was invaded by G.U.N. soldiers. Before the ARK could be shut down, Maria sent Shadow down to Mobius, before she was killed by the soldiers and Gerald Robotnik was incarcerated and later executed. Shadow was later captured and put into a comatose stasis for at least fifty years.
One day, Dr. Eggman found him and released him from the stasis, and is told to come to the ARK with the chaos emeralds. After Eggman goes to the ARK, Shadow tells him about the Eclipse Cannon and its power, and are greeted by Rouge, who agrees to help the two find the chaos emeralds. The three eventually find the Chaos Emeralds, and succeed in re-powering the ARK. Before they can utilize the cannon, Dr. Eggman discovers the truth behind his grandfather, and learns that the ARK was set to crash into the Mobius. After everyone learns about it, they set off to make a plan to stop the crash. However, Shadow initially refuses to help, before Amy convinces him to help by unwittingly reminding him of his promise he made to Maria. But before he can help, he is stopped by the Biolizard, the prototype Ultimate Life Form. After he defeats it, the Biolizard attaches itself to the ARK, and Sonic the Hedgehog and Shadow both use the newly-reattained Chaos Emeralds to go into their super forms and stop the ARK from crashing, it succeeds, but Shadow is sent down to Mobius, seemingly dying of re-entry.
Despite everyone believing Shadow to have died, he survived his re-entry, but lost his memory from the impact. In an attempt to re-discover himself, he encountered Black Doom, and learned that the alien's DNA was used to create him. After learning this, Black Doom possesses him to stay put, but the hedgehog is shown a clip of Gerald Robotnik explaining to him that the Eclipse Cannon was meant to destroy a Black Comet before it could allow the Black Arms to destroy Mobius. He is given the motivation to fight back with the chaos emeralds, and eventually triumphs. He then returns to the ARK and uses the Eclipse Cannon for its intended purpose. From there, he became accepted by the citizens of Mobius, and became one of Sonic's closest allies.
Season 2 and 3
Despite having thought that Infinite had been defeated by Sonic back on Mobius, he learns that the jackal had returned to bring terror to the Locked Rooms. He tracks him down in another room, finding the jackal terrorizing The Shadow Team (Originally consisting only of Shadow Assassin, Spyro and Robin), and defeats him, causing Infinite to leave in frustration. Reluctantly, he joins the team to help them track down and get rid of Infinite once and for all. On their way, they stumble upon an abandoned lab, and awaken Dark Knight Super Monkey as they re-activate it. After Super Monkey introduces himself to the team (Including his old friends Spyro and Robin, who didn't recognize him), the five are attacked by Killer Robots. Shadow orders the other four to distract the Killer Robots while he destroyed the cloners, but him destroying one alerts the robots, and they re-focus onto him. Shadow is forced to change his plans, and simply destroys all of the robots and cloners with a Chaos Blast. This costs him a lot of energy, however, and the five have to rest uncomfortably in the lab, which lacks a bed of any kind.
- Chaos Control
- Allows Shadow to warp or freeze time for a moment or two.
- Chaos Spear
- Allows Shadow to throw a projectile of pure energy which can pierce it's targets and destroy them (Also known as a bean burrito!)
- Light Attack
- Charges up light energy and gains an aura around him which allows him to attack people at light speed.
- Green Chaos Emerald
- Shadow's use of warping or Chaos Control
- Hover Shoes/Air Shoes
- Allows Shadow to run in style, making him not only fast, but cooler as well.
- Allows him to dash slightly faster.
- ThePlantedAKEE added him because Moon Snail uses Sonic, and Shadow was the next best thing.