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Netherop, identified by the Covenant as Neska and N'ba, is a greenhouse planet located within the Polona sector's Ephyra system. Netherop was once home to a civilization of intelligent beings, but has been uninhabited for centuries.
Many centuries ago, Netherop was home to an intelligent civilization. This civilization ended, however, due to the great increases in temperature that resulted from greenhouse gases. A survey was done by the UNSC of Netherop, but was cut short by the planet's hostile environment. The Military Survey of Uninhabited Planets would list Netherop as uninhabited, marginally survivable, of minimal strategic value with no exploitable resources. Though the survey notes suggested that a properly equipped survey team should return, a classified ONI addendum listed the planet as possibly abandoned, suggesting that the survey had found anything from an old Colonial habitability probe to the presence of terrain features that could've been artificially constructed. Frederic-104 would later guess that the survey had been electronically added to the MSUP by some clerk who only read the part about minimal strategic value and no exploitable resources and as such, the assessor's recommendation went unread and thus not acted upon.
At some point in probably the twenty-fifth century, a group of pirates with Insurrectionist leanings were marooned on the planet. Though they weren't expected to survive, the pirates and their descendants managed to make a living on Netherop, coming to call themselves the Castoffs.
On March 5, 2526, a single Covenant frigate, the Radiant Arrow, was holding position in orbit around the planet until it was boarded by three teams of Spartan-IIs, forcing the ship's self-destruction at the hands of its shipmaster.
In June 2526, the UNSC returned to Netherop to capture the Steadfast Strike, a Covenant frigate apparently downed there. However, this was actually a trap by renegade Covenant Fleetmaster Nizat 'Kvarosee who planned to plant Luminal Beacons amongst the human forces so that he could locate and destroy ONI and redeem himself in the eyes of the Hierarchs and their gods. However, due to 'Kvarosee's renegade actions, the Silent Shadow and the Fleet of Swift Justice chased him to Netherop, leading to a three-way battle on and above the planet. Much of 'Kvarosee's forces were decimated, but two of his ships, including 'Kvarosee's flagship the Quiet Faith escaped. The Silent Shadow eventually destroyed the Steadfast Strike and exiled 'Kvarosee and his few surviving followers on Netherop after removing their armor. At the same time, the surviving human forces pulled out aside from Lieutenant Commander Amalea Petrov who intended to create a deep-operations base on the planet.
To complete 'Kvarosee's exile, the Silent Shadow established a minefield of self-targeted plasma torpedoes around Netherop, preventing even a drop pod from getting through to land on the surface. In this fashion, the Silent Shadow ensured that no loyal Shipmaster could ever rescue 'Kvarosee who witnessed the destruction of five ships attempting to do so. This also cut the UNSC off from the planet permanently though they rescued many of the Castoffs and relocated them to Gao at the Castoffs' request.
Netherop appears to be covered in a pall of dingy brown clouds, many of which rapidly expand in various swirls. Netherop's atmosphere produces a thick corona and its mesosphere creates a pearl-colored haze. A survey of the planet lists it as uninhabited, marginally survivable, of minimal strategic value with no exploitable resources. Daylight on the planet, at least at the latitude visited by Blue Team, lasts twenty-three hours and five minutes. The planet's night also appears to last a long time, so long Nizat 'Kvarosee considered it to be interminable.
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