Emerl is a Sonic character that was created by the Nocturnus Clan from Sonic Chronicles: The Dark Brotherhood. Claiming to be the Ultimate Gizoid, he was sealed away in the Twilight Cage. 4,000 years later, Doctor Gerald Robotnik found him and tried to deactivate his destructive powers, but fails to do so. He, instead, gives him the same qualities as Shadow the Hedgehog with his granddaughter, Maria Robotnik's soul.
In Sonic Battle
Emerl was a robot that was thrown away by Dr. Eggman and discovered by Sonic and co. Sonic and Tails trained Emerl to become a fighter. In the game, they use Chaos Emeralds to power him up (which Gameplay wise, increased his skills.) and was eventually able to speak. Emerl copies the personalities and abilities of the many that he encountered (Sonic's love for speed, Rouge's love for the Chaos Emeralds, etc.). Towards the end of the game, Emerl fights Dr. Eggman and defeats him. Thinking the Doctor learned his lesson, Emerl turns his back, and Eggman fires the Final Egg Blaster at some nearby stars. Emerl's data and personality was deleted and he became a weapon of mass destruction. Sonic, hoping to bring Emerl back with the Master Emerald, uses a teleporter to the Death Egg and tries to stop him. Emerl is defeated and says his last goodbyes, thanking Sonic for everything. Emerl then blows up, leaving nothing but the Chaos Emeralds behind with him.
In the Sonic X anime
In the Sonic Battle arc of Sonic X, Emerl is activated by one of the Doctors henchmen, Bokkun. Bokkun activates Emerl to disctract Sonic while the Doctor escapes prison. Emerl goes with Sonic and Co. and stays with them, bonding with Cream the Rabbit. As he see's the gang in action, he copies their abilities. Emerl enters a fighting tournament with several other Sonic characters, naturally winning. Emerl wins and absorbs the Chaos Emerald, and his original programming is restored, becoming a weapon of mass destruction. Cream the Rabbit manages to defeat Emerl, but because she defeated a friend of hers, she started to cry. Because that was the last thing Emerl copied, he learned how to cry (his tears were oil in the Japanese version).