From Halopedia, the Halo wiki
The Nereus system is a planetary star system.
Nereus is the next star Earthward from the Tisiphone system and shares a sector with it. It is an uninhabited system of ice balls and dust-smothered rocks that makes for a perfect hiding spot for pirates.
In Decmber of 2553, a Banished flotilla was holding in orbit above Nereus X, which was being used as a temporary hideout. Rear Admiral Serin Osman had a prowler in the system observing the ships and was considering giving the order to launch an operation against them on December 8, pending the determination of an investigation concerning the murder of Graselyn Tuwa and the potential kidnapping of her family.
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