4-LOM is a droid bounty hunter, one of the six aboard the Executor in The Empire Strikes Back (1980). StarWars.com gives the origin in two sentences: "A rusty droid with insectile features, 4-LOM was originally a protocol droid, but logic glitches allowed him to escape his programming and become a bounty hunter. That proved a perfect occupation for the cold, calculating mechanical."
An accident that became a career
The premise is quietly one of the most unsettling in the setting. 4-LOM did not rebel and was not reprogrammed; his constraints simply failed, and what was left underneath turned out to be very good at hunting people. Where IG-88 was built to kill, 4-LOM was built to translate and arrived at killing by drift.
The face
The insectile head is a production artefact — the costume borrows heavily from the design language used for the Gand — and it has the useful effect of making him and Zuckuss read as a matched pair on screen long before any story explained why they work together.
Trying to learn intuition
M. Shayne Bell's Legends novella in Tales of the Bounty Hunters (1996) makes him the point-of-view character in a partnership with a mystic. 4-LOM watches Zuckuss perform findsman rituals and tries to derive the method, collecting raw data in the hope of unlocking a process that is explicitly not reducible to data. It is a Star Wars short story about the limits of inference, which is not a sentence one gets to write often. The character background — 4-LOM as a former ship's purser — originated in West End Games' Galaxy Guide 3 (1989).
