Dyer, a human male, holding the rank of Colonel, was a member of the Galactic Empire. He fought against the Alliance to Restore the Republic during the Galactic Civil War.
Dyer was stationed on the surface of one of Endor's moons as the commanding officer of the Death Star's shield generator bunker. This was during the Galactic Empire's construction of a second Death Star in orbit around the moon.
During the Battle of Endor, the Rebel Alliance launched an assault on the still-incomplete Death Star. As part of this attack, they dispatched a squad to Endor's surface, which successfully infiltrated the bunker with the goal of destroying it. Dyer, along with a contingent of Imperial forces, engaged the rebels as they were in the process of planting explosive charges within the bunker. However, General Han Solo incapacitated the colonel by throwing a toolbox filled with explosives, causing him to fall over a railing into the generator room below. Ultimately, the rebels succeeded in destroying the generator, which led to the destruction of the Death Star II.
Dyer's physical characteristics included brown hair, brown eyes, and a light complexion. He was armed with a DL-21 blaster pistol.
Colonel Dyer's debut was in the 1983 movie Star Wars: Episode VI Return of the Jedi. He was played without credit by Ben Burtt, who also served as the film's sound designer. The reference book Ultimate Star Wars, published in 2015, established the character's name as canon.
Dyer's inclusion in the film happened relatively late in production; he wasn't present in the original revised third draft of Return of the Jedi, nor was he in Star Wars: The Annotated Screenplays. The script combined the lines of Dyer and Lieutenant Renz, with the character shouting "Freeze! You Rebel scum" simply identified as "Commander." However, in the latter, Renz was called "Commander," while Dyer was referred to as "Imperial officer."
Barrie Holland, the actor who played Renz, mentioned that filming the scene with Dyer and Renz was challenging because director Richard Marquand had disagreements with his assistant director and first cameraman. It took "several beats" to film the scene correctly, and Holland initially thought a stuntman played Dyer before learning that Ben Burtt played the role.
In the audio commentary for the 2004 DVD release of Return of the Jedi, Burtt discussed his cameo as Dyer. The scream Dyer makes when he falls into the generator room was intended as an attempt to replicate the Wilhelm scream, which Burtt has tried to incorporate into all the films he's worked on.