The Warrior

The Warrior was a Vault monster that was created to protect Pandora from being opened.

History
As the Eridians were in the process of building Pandora, many other races attempted to interrupt the construction, hoping to appease the Destroyer and save themselves. The Warrior was created to prevent these attacks, which it did successfully. The Eridians placed it in its own vault, where it rested, ready to defend against other trespasses on Pandora.

After opening the Vault of the Sentinel on Elpis, Handsome Jack saw a vision of the future, including the existence of the Vault of the Warrior. Jack intended on controlling it in order to wipe the bandit population from the planet.