XB-55

XB-55 is an Enclave Sentry bot in The Enclave research facility in 2103.

Background
XB-55 is a security unit programmed by the Enclave to protect SODUS from any who would try to harm her. During the destruction of the facility XB-55 was presumably left inactive. In 2103, when the Vault 76 Dweller - accompanied by Knight Daniel Shin and Paladin Leila Rahmani - enter SODUS's chamber the AI will upload its programing into XB-55 and fight the trio.

Quests
Over and Out: SODUS uploads herself to XB-55 and acts as the end boss of the quest.

Appearances
XB-55 appears only in Fallout 76, being introduced in the Steel Dawn update.