Ultra Magnus (aka Magnus and Ultra Mammoth) feels he is a soldier and nothing more.
He very much prefers taking orders to giving them, and even avoids opportunities for higher responsibility. But when he is forced into those opportunities, he betrays his real talent for the job. He's strong, resolute, dependable, selfless, and courageous.
Sadly, Ultra Magnus is the only Autobot who doesn't realize this.
The Autobots on Earth returned to Cybertron once Optimus Prime's team had defeated Galvatron, the D-Void, and the Decepticons. Feeling that the Autobots were no longer wanted on post-war Cybertron, Ultra Magnus decided to accompany Rodimus and Drift on their quest to find the Knights of Cybertron.
He joined the crew of the Lost Light as Rodimus's second-in-command, but soon started to become increasingly petty about minor infractions and had many, many reservations about those who had signed up for the quest. Magnus's troubles on the Lost Light started when an accident at launch caused the ship to quantum jump to a random point in space.
Magnus was among those interviewed for Rewind's documentary about life on the ship, "Little Victories". He used his authority to censor the parts that made him look silly. But it would be some time before the video would be seen by the other crewmembers, given what was about to happen...