Emerl is a character who first appears in the game Sonic Battle. He is a robot referred to as Gizoid by the ancients that is said to be over 4,000 years old, and the cause of the destruction of the Fourth Great Civilization, according to Professor Gerald Robotnik. He is found by Sonic the Hedgehog on Emerald Beach who develops an instant "Link" with him and because of this "Link", will not take orders from anyone else, unless Sonic commands him to.
Sonic takes him to his friend Miles "Tails" Prower to fix up because he didn't know how to speak, and could barely move. Afterwards, Rouge the Bat appears, who plans to train him to become the ultimate robot thief. Sonic tells Tails what he found and Tails fixes Emerl up, in addition to examining the robot and finds an amazing discovery. He finds that Emerl is in fact a legendary battle weapon with great fighting capability, but needs Chaos Emeralds to regain its lost power as a battle weapon. He also discovers that Emerl has a built-in AI system which allows him to learn fighting styles from others. Soon after, Sonic finds Rouge who is trying to think of a way to steal Emerl. Sonic defeats her and she flees after telling Sonic that Dr. Eggman wants to steal him as well as Shadow the Hedgehog. He goes back and tries to tell Tails what he found, but is instead attacked by a strange silver robot who looks almost exactly like Emerl. Sonic destroys it and finds Tails and asks him if he and Emerl are okay. Tails replies yes and tells Sonic about what he discovered about Emerl. When he tells Sonic this, Sonic decides that he and Tails should train him in combat. Pretty soon, he learns some of their attacks.
Afterwards, a news bulletin comes on television saying that a mysterious silver robot has appeared in Night Babylon. Tails says that it's another fake "Emerl".