Shadow the Hedgehog

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.

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)
His theme

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.

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.

Chronicles of the Children of Megatron
Shadow is a bodyguard to Arukenimon.