Shield 0459 was a Forerunner Shield Installation deep in uncharted space. A variation upon the Shield World concept, originally built as a Forerunner Warrior-Servant outpost, it was repurposed to protect sentient lifeforms from the effects of the Halo Array and the Flood. It also served as a port for a fleet of Forerunner Ships. Despite the fact that the Shield Worlds were military strongholds, and later as a haven from the Array and the Flood, the external surface was heavily infested with Flood biomass, with forms of various types freely roaming across the surface. Sentinels were a rarity on the outside, but this changed within the center, where the many Forerunner constructs worked to prevent the Flood from claiming the interior as well.