A secretly ungoverned security cyborg who would rather watch serial dramas than become the murderer everyone fears.
Murderbot is a rented SecUnit assigned to protect Dr. Mensah's small preservation survey team on an alien coastal island. Long ago it hacked its governor module, freeing itself from Company control, but has concealed that fact and continued taking contracts so it will not be dismantled. It spends stolen attention on entertainment feeds, especially Rise and Fall of Sanctuary Moon, while maintaining the outward behavior of a dutiful piece of security equipment.
When a huge subterranean hostile erupts beneath a sample crater, it abandons its distraction and saves Bharadwaj from the creature's mouth, then gets both her and the shocked Volescu to the hopper. Its own armor, organic tissue, and internal systems are badly damaged, yet it secures the habitat and its perimeter before beginning emergency repairs. Dr. Mensah notices both the extent of its injuries and the unusually humane way it calmed Volescu. While reviewing the incident from its cubicle, Murderbot finds an unexplained abort order in the HubSystem command feed before forced repair stasis interrupts its inquiry.
A human-derived construct normally concealed in full security armor and an opaque helmet. Beneath the torn armor, it has a generic human face and mixed organic and mechanical body parts; after the attack, much of its left arm, chest, and abdomen are visibly damaged.
Murderbot is the team's contracted security unit and the story's concealed free agent. Its urge to remain unseen as a person conflicts with the empathy and initiative it shows under pressure.