Mickey is an Expendable on the Drakkar expedition to Niflheim, meaning he performs dangerous tasks and is cloned with uploaded memories whenever he dies. He currently exists in his seventh iteration after six agonizing deaths. Originally from Midgard, he joined the mission to escape debt, bringing along a deep interest in history rather than the socially preferred STEM fields.

Mickey8 is the newly printed clone of Mickey Barnes, created when the colony believed Mickey7 died in an ice crevice. He shares Mickey7's memories up until the last backup six weeks prior. He possesses a slightly more ruthless survival instinct than his predecessor and actively tries to establish his own life within the colony's tight constraints.

Nasha is a skilled combat pilot for the Drakkar expedition. She grew up on Midgard as the child of refugees from the failed New Hope colony, leading her to seek a fresh start on Niflheim. She provides crucial emotional stability for Mickey, sitting with him through horrific deaths and treating him as a complete human being rather than disposable equipment.

Berto is a tall, muscular combat pilot and Mickey's handler on the expedition. He excelled in academics and sports on Midgard before securing a highly coveted spot on the Drakkar. His relationship with Mickey is strained by his pragmatic, sometimes selfish decisions regarding danger and resource management.

Cat is a 34-year-old security guard on the Niflheim colony. She initially knows little about Mickey aside from his status as an Expendable. After surviving a dangerous encounter alongside him, she begins to see him as an individual rather than a disposable asset, prompting her to question the ethics of his existence and her own mortality.

Marshall is the ground commander of the Niflheim expedition. He belongs to the Natalist Church, a religious sect believing each body houses a single soul, which makes him view Expendables like Mickey as soulless abominations. He uses his authority to heavily restrict resources and actively endangers Mickey on missions to validate his own prejudiced beliefs.

Dugan is a biologist working on the Niflheim colony. He provides early explanations about the Natalist Church to Mickey. He maintains a distinct separation from Mickey out in the field, believing his own life holds more value because he cannot be reprinted.

Darius is a dangerous loan shark on the planet Midgard. When Mickey placed a bad bet against Berto in a professional sports tournament, Darius sent enforcers to collect the debt, directly motivating Mickey to sign away his life as an Expendable to escape the planet.

Jemma is the woman responsible for training Mickey in his duties as an Expendable. She attempts to psychologically prepare him for his continuous cycle of death by discussing philosophical concepts like the Ship of Theseus and forcing him to undergo a traumatic mock execution.

Burke is a medical officer on the Drakkar expedition. He has a clinical detachment regarding Mickey, having previously killed iterations of him three times during various medical experiments required for the colony's safety protocols.

Darren is a security officer who loses a bet of his caloric rations to Berto. Angry over the loss, he instigates a physical brawl that ultimately draws unwanted attention from the colony's command staff.

Gillian is a security officer and Cat's roommate on the Niflheim colony. Her sudden death during a creeper attack deeply affects Cat, emphasizing the constant danger the colonists face outside their protective dome.