The UNSC Eternal Peacekeeper (informally referred to as the Peacekeeper) was built alongside the UNSC Pillar of Autumn as it's sister ship, along with the UNSC Dawn Under Heaven. Both the Peacekeeper and the Autumn were prepared for deployment on August 30. However, before they could depart from the Epsilon Eridani System, they were recalled to Reach; the UNSC fleet was mustering in preparation for an imminent Covenant attack on the planet.
During the later half of the battle, numerous surviving Spartan-IIs and Spartan-IIIs, such as Riley-G311, Ryder-G231, Matthew-123, and Rowan-090, made their way to the vessel as escape from the horrific battle, with little anticipation for being ferried directly to another battle afterward. After the battle, while the Pillar of Autumn made a random slipspace jump to Installation 04, the Peacekeeper was ordered to follow the Covenant fleet by an unknown ONI Section Zero operative. This ultimately lead the Peacekeeper to Hope, where the ship deployed a small army of marines and Spartans, before sending out an emergency transmission requesting backup. Many UNSC ships rushed to it's aid, however, the Peacekeeper was destroyed by an overhead Covenant supercarrier before receiving help.
