The system of worlds orbiting the star of Esoterra are controlled by the Adeptus Astartes of the Imperium of Man. This system was hidden away by warp storms for millenia and was sheltered throughout all ages from contact from all sentient beings in the galaxy with the exception of the peaceful Marbongi people, who have since taken to the stars and abandoned their homeworld due to a false belief that their star was dying (Imperial astronomers predict the star will live hundreds of millions of years yet.) Since then these worlds have lain dormant until the arrival of the Demiurg and their mining craft, and eventually the Tyranids and Humans.