The Empyrean Sentinel is an ancient, eldritch being created by the Eridians to guard the Vault of Elpis. It appears as a humanoid, multi-faced warrior with a body seemingly carved from stone. When damaged sufficiently, its body grows exponentially in size, utterly dwarfing any guardian.
Little information about The Sentinel is presented until Jack's Vault Hunters enter its Vault and encounter it themselves. Upon their arrival, The Sentinel appears through a portal to stand in their way, and must be defeated to unlock the Vault's secrets.
After the main story has been completed, The Sentinel can be fought again in its original form, or reincarnated as a raid boss, renamed The Invincible Empyrean Sentinel. It can be summoned by placing 20 pieces of Moonstone on the pillars located in front of the entrance to the Vault in Eleseer, once The Bestest Story Ever Told, given at the bounty board located in Concordia, has been accepted. After completing the mission, The Invincible Sentinel can be battled repeatedly, for the cost of 20 Moonstone every time.
- Main article: The Beginning of the End
- 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.