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.
According to an official poll, Shadow is the second most popular character in the series, behind only Sonic himself.
Shadow is voiced by Jason Griffith
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.