Shadow the Hedgehog (シャドウ・ザ・ヘッジホッグ Shadō za Hejjihoggu) is a fictional character from the Sonic the Hedgehog series. He is an anthropomorphic hedgehog/Black Arm hybrid and the arch-rival of Sonic the Hedgehog. Shadow was created as the "Ultimate Life Form" (究極生命体 Kyūkyoku Seimeitai?) by Gerald Robotnik, using the DNA of Black Doom, and is the final result of Project Shadow. His purpose was to provide ways of developing cures for deadly illnesses that had no cures, namely for Gerald's granddaughter Maria Robotnik, but he was captured and put into stasis by the military when he was deemed a threat to humanity.
Fifty years later, Shadow was released by Dr. Eggman to help him conquer the world. Initially, Shadow sought to destroy Earth to avenge Maria, who had been killed by the military, but was persuaded to help save it from Gerald's doomsday plans. In the process, Shadow lost his memories and he sought to uncover his past, which brought him into contact with the Black Arms. Ultimately, Shadow thwarted Black Doom and saved the world. From there, Shadow continued his mission to protect humanity by becoming a special agent of GUN.
Shadow is sharp-witted, always on edge and has a strong sense of purpose, willing to accomplish his goals by any means necessary. Essentially a dark version of Sonic, Shadow can match him in both speed and skill, and possesses the ability to use Chaos Control with a Chaos Emerald. While preferring to work alone, he will help Sonic and friends when necessary.
Shadow is voiced by Kirk Thornton
Legends of the Multi-Universe (Menslady's Story)
Shadow came along with Sonic and Silver to aid Team Prime. During this, he rescued Sailor Mini Moon from Freddy Krueger. The thing was that he didn't care how grateful she, Sailor Moon and Tuxedo Mask were. However, he later ended up being a friend and mentor to Sailor Mini Moon.
At the end of the story, Shadow was reunited with Maria, who had been revived by Primus, Arceus and the two Eternal Dragons.
The P Team Storyline
Wrath of the God of War
Shadow returns with Sonic and their friends against Ares and the other villains.
Meister of War
Shadow returns helping Sonic, Knuckles Riso, and others against Zeus and other villains.
The Legend of Maka Albarn
Shadow appears in this story and aligns himself with Slade and his forces against Eobard Thawne and his legion and laters join the fight against Bill Cipher, Toffee and the cult.
☀Shadow joins Slade and his team after they show up in the future, he is a very distant from his allies, but he still works to help and fight the legion, even increasing his efforts when Mephilles get involved. Shadow also manages to avoid getting being turned into a trophy and works to take the throne back from Thawne, before fighing Toffee and Bill Cipher. He works with the others to make a weapon powered by Phenoix Downs and does the most farming for the gang. Before single handily taking out a third of Toffee and Cipher's forces. After the fight is done and the spear of destiny changes reality and Shadow departs from the group.
LOTM: Darkness Incarnate: Liberation of Mobius
Chronicles of the Children of Megatron
Shadow is a bodyguard to Arukenimon.
Shadow made his debut in Ultimate Story 2. He attended a Mushroom Kingdom Double Dash Grand Prix with Rouge as a spectator. When Cream's car was wrecked by an "unfortunate accident" the race was nearly cancelled as they were short one car. Shadow and Rouge decided to step up as replacement racers in order to keep the Grand Prix going.
After the Grand Prix, Shadow officially became a full-fledged character to the Ultimate Story and a reliable ally to Fox and his friends. He especially has a great deal of respect towards Fox. He also became close friends with Slippy, as he had promised to bring back something that Shadow had lost a long time ago. His powers have come in handy many times.
He pairs himself a lot with Falco and has very often been a trusted partner and comrade to him along side Sonic.