The homeworlds of the Covenant are filled with many extremes, both beautiful and dangerous - the triple-star configuration which bombarded radiation to Sangheilios, the bone-chilling Methane atmosphere of Balaho and the hostile fauna of Palamok. Doisac is no different, having its fair share of extremes - life-filled rainforests established next to hot volcanic terrain which cover more than half of the surface being the biggest expression of that. Hospitable yet hostile, comfortable yet boiling hot, Doisac's harshness gives rise to its natives that eventually resulted to its own sentient species, the brutish Jiralhanae.