The Cultists were radical, extremist offshoot of Adam Hale's White Faction and Marauder state. Their charismatic leader on the other hand, Adam Hale, had ties to the long vanquished Earth Defense Force and played a major part in War of 2150 and particularly the Battle of Bakhuysen Trench when he first attempted to destroy the Terraformer. Whether the Cultists share a stronger link with the White Faction or whether Hale simply co-opted another group to suits his aims is unknown.
Under Hale's leadership, the Cultists went to war with the Red Faction and forced everyone to take shelter beneath the surface after destroying the Terraformer and wrecking the planet's weather. Hale was believed to have died during this battle and the threat the Cultists posed nulified, but he survived.
The Cultists still lead by Adam Hale would emerged once more after tricking Darius Mason into destroying the Seal and unleashing the Plague Armageddon upon Mars and the faction as a whole continued well the the armageddon with some member likely surviving after the Plague threat was exterminated.