The Fatex Imperator (Doom Emperor/Angel) Temple is the religious body that governs the Heralds of Coming Doom and any other Chapters which embrace worship of the Doom Angel and adopt his Aspects of the Coming Doom. The Cult shapes the beliefs, lore and traditions of its followers and forms a pivotal role in preserving and directing the sacred psychic bond that the followers of the Temple form with Bororus Prime, the most powerful manifestation and store of the Doom Angel's power. It is this link which is reputed to be the source of many of the supernatural abilities displayed by the Heralds and their Temple Brothers.
The Temple upholds direct communication of the Doom Angel's will to his faithful, allowing the Seers and Chaplins to see his visions and pass his words on to the Brothers of the Chapters of the Temple.
The Temple organises worship of the Emperor in is incarnation as a deity of destiny and destruction who sweeps all before him in to annihilation. This incarnation is known as the Doom Angel and represents the needs of humanity to wage war for survival in its purest form and the manipulation of conflict through the Aspects of the Coming Doom to achieve this dark god's will. The goal of the Angel is the extinction of every other sentient race to destroy Chaos and protect Humanities future, no cost is too high and no action too vile to achieve the Human Races' guaranteed survival.
To attain this the Doom Angel intructed his first true followers, the Heralds of Coming Doom, in the ways of the four Aspects of Doom: Fire, Death, Terror and Vengeance. These Aspects are survival, conflict and fate in its most primeval forms and allow believers to master powers and techniques to dominate any battlefield, to decimate any opponent and crush them into the dirt. Execution of the creeds provided by these Aspects allow the faithful of the Temple to control the fate of Humanity and by extension, its enemies through war as they can force events through the horrors, victories and defeats caused by conflict. For example the Faithful may attack an Exodite world to force a Craftworld to take action, drawing out a conflict which ultimately is beneficial to Humanity for reasons ranging from destroying the Eldar military might to simply 'training up' Battle Brothers.
The ability to predict the future is not a strong ability amongst the Temple Brothers, but rather any insights are provided by the Doom Angel and then they must be translated, much like how Astropaths can receive visions, seemingly at random.
Each Temple Chapter has four cults, one for each Aspect and the Great Seers of each are members of the Temple Hierarchy which is aided by the Chaplins and are responsible for all the Temple's roles and activities. The Temple upholds that each Cult must abide by the creeds of its respective Aspect, but must learn some of the creeds and techniques provided by the other Aspects, albeit in a limited fashion. Each Cult therefore specialises in an area of warfare and tactics as directed by the Temple and its Aspect. Fire Cults form the ranged and tactical corps and elite of the Temple Chapter, while the Vengeance Cults form their close quarters and fast attack counterparts. The Terror Cults are the sabotage and psychological specialists of the Chapters and the Death Cult oversees the First Hosts of the Chapters.