Beast Megatron is a Predacon who arrived in the timeline of the original Transformers series through a phenomenon known as the Blastizone, following the original Megatron's disappearance. He swiftly claimed leadership of the Decepticons by defeating Starscream in combat.

A highly intelligent and strategic commander, he is manipulative and consistently employs complex schemes, frequently exploiting the treachery of his own subordinates to further his goals. His actions are driven by a significant ego and a pronounced flair for the theatrical, often preferring elaborate plans over simpler solutions.

In the Robot Masters narrative, his leadership was contested by the arrival of Reverse Convoy, later revealed to be the original Megatron reborn as Rebirth Megatron. Despite this rivalry, Beast Megatron and Rebirth Megatron combined their efforts, executing a dual attack against their opponents during the conflict.

He transforms into a purple Tyrannosaurus Rex mode, noted for its screen-accurate appearance relative to his original Beast Wars depiction, though with potentially lighter shades of purple. His robot mode features a head sculpt that pays clear homage to the original Generation 1 Megatron, and a Decepticon insignia is present on his left shoulder, a detail attributed to the convergent nature of the Robot Masters series.

His background prior to these events identifies him as a rogue Predacon field commander who rejected the Pax Cybertronia peace treaty. He stole the Golden Disk, which contained a message from his namesake, and traveled to Earth with the intent to alter history and secure Decepticon victory in the Great War.