"If you're not here as a miner, and you're not here to join up with the resident rebel scum, then I can't understand why you of all people would bother to come here."
―Cpt. Jonny Ashfield.
Green Hills, the name literally referencing the numerous deposits of Sulphuric compounds, is a former colony located next to the boundary that marked the end of human-explored space. Also locally known as Barrens, Green Hills was founded by a colonial effort backed by the BXR Mining Corporation as a way to access the colony's mineral richness. However, along with its neighbours Harvest and Second Base, Green Hills would be far better known for being one of the first casualties in the war against the Covenant.
Prior to its glassing, Green Hills was an obscure mining world that was avoided by most humans for two reasons. Firstly, the planet was host to a hostile environment, with its atmospheric composition, high environmental heat and its low density causing a large number of illnesses in humans that were not protected within its shielded terraformed zones. The main reason, however, is that the living conditions were ruined by BXR's monopoly over the planet. The population of the cities lived in corporate servitude, deprived of the most basic human rights, while the farmers who lived beyond the suburbs had to undertake increasingly dangerous jobs to make a living. This gave the colony its raised crime rate and terror attacks, both of which were effectively put down by BXR's mercenary armies.
Currently, the planet is utterly uninhabitable, with the Covenant bombardment clouding the surface with trillions of tonnes of greenhouse gases and manufacturing by-products that were previously hidden below the surface. Being incredibly difficult to reterraform back to its previous state, not to mention expensive to mine in its current state, it has remained at the bottom of the UEG's reconstruction priorities, to nobody's surprise.