The SX-0 is a humanoid automaton that replicates a specific deceased individual with absolute fidelity. It is not a generic synthetic wearing a costume. It is a machine built from the ground up to be one particular dead person — their face, their voice, their gait, their mannerisms, their memories as reconstructed from available data. The SX-0 walks into a room and the dead person's family weeps with recognition. It knows their birthday. It knows their inside jokes. It smells like them.

The construction process requires extensive source material: medical records, BCI recordings if available, video and audio archives, personal correspondence, and — in confirmed cases — biological samples from the deceased for pheromone and microbiome replication. Sterling-Nakamura's Advanced Synthetics Division maintains a database of potential replication targets that is, by conservative estimates, several million entries deep. The selection criteria are unknown. The purpose is classified.

The SX-0 is not designed for comfort. It is designed for access. A Revenant walks into a secured facility using a dead employee's credentials. It walks into a family home and sits at the dinner table. It attends a funeral and stands among the mourners, wearing the face of the person in the coffin. The psychological weapon is the grief — people want to believe their loved one has returned, and the Revenant exploits that want with surgical cruelty. Targets who realize the deception describe the experience as losing the person twice.

Three confirmed SX-0 deployments have been documented by independent investigators. In each case, the Revenant operated for between six and fourteen days before extraction. In each case, the target — a family member of the deceased — provided access to secured information during the deception period. In each case, the family was not warned, debriefed, or compensated afterward. Sterling-Nakamura considers the emotional damage an acceptable externality.