The Sentinel is encountered during the mission The Beginning of the End. Little information about the Sentinel is presented until Jack's Vault Hunters enter the Vault and encounter it themselves. Upon arrival inside the Vault, the Sentinel appears through a portal and must be defeated to unlock the Vault's secrets.
- Main article: The Beginning of the End
- After completion of the main story, the Sentinel can be fought repeatedly in its original form, by returning to the Vault in Eleseer.
- The Sentinel bears great resemblance to the Asuras found in Buddhist texts. Asuras are the lowest form of deity - wicked, multi-faced beings obsessed with the vices of the world.