Complex sentence: At the same time, an Autobot drifter named Sideways enters the fray, but soon reveals his true allegiance to the Decepticons after he betrays Hot Shot, allowing the Star Saber to fall into the Decepticons' hands.
Split into simpler sentences: At the same time, a drifter named Sideways enters the fray, siding with the Autobots, but soon reveals his allegiance to the Decepticons. Sideways manipulates Hot Shot, allowing the Star Saber to fall into the Decepticons' hands.