- Extremely powerful Forerunner drone
- The Ark's Retriever Sentinels are among the most powerful Forerunner drones,
- their primary purpose being the mining of the Foundry in the creation of Halos
- and Ark maintenance. However, like all Forerunner drones, they can also be used
- to defend the Ark by turning its sentinel lasers on anyone who threatens it.
- The Retriever Sentinels played an important part in repairing the Ark after the
- events of 2553 in the final battle between the UNSC and the Covenant. UNSC
- scientists at the Henry Lamb Research outpost reactivated the dormant
- retrievers and watched in awe as the Ark was restored to its former glories.
- Sadly, war has once again come to the Ark, but the Forerunner drones built to
- protect it will stand fast and push back against any and all invaders.