Complex sentence: Sometime before the events of the storyline, Dr. Eggman builds a robotic assistant based on, and using parts from a Emerl, named Gemerl, designed to be a loyal, obedient copy of Emerl.
Split into simpler sentences: Sometime before the events of the storyline, Dr. Eggman builds a robotic assistant based on and using parts from Emerl named Gemerl. Gemerl's designed to be a loyal, obedient copy of Emerl.