Ultra Magnus generally appeared as a chief lieutenant to the leader of what fictional group of sentient robots?
Optimus Prime Optimus Prime is a fictional character from the "Transformers" franchise. He is the leader of the Autobots. A fictional group of sentient robots that can transform into other forms (e.g: cars and other objects) He is the most iconic of the Transformers, being frequently featured in Popular Culture.
Machinesmith Machinesmith (Samuel "Starr" Saxon) is a fictional supervillain appearing in American comic books published by Marvel Comics. He specializes in robotics, and is able to make convincing doubles of other superhumans. His own mind was later transferred to a robotic body.