Despite never formally taking stewardship of the Throne, High Exarch Masood al-Awar was a prominent figurehead during the Dark Ages, maintaining the Messianic faith despite the near collapse of the Empire. Masood’s eventual assassination led to him being revered as a martyr and sacrificial messiah figure. His informal admirers later crystallized into the Masoodites, who codify the long dead High Exarch among the ranks of past Emperoxs.
The Masoodites are not particularly favored among their brethren in the High Church, seeing as how their core tenant runs contrary to the recognition of the Messiah through a formal process. Masood al-Awar is still seen as an example of Piety for many priests, though fervent enemies of the Masoodites have gone so far as to decry the Exarch as a usurper and a sinner.
Masoodites tend to view all High Exarchs in a more devout light, since they believe each leader of the High Church holds within themselves the potential spark of a prophet, not one of which has been revealed since the death of their idol.
Predestination is a prevalent theme in Masoodite teachings - anyone who is so worthy to watch over the Empire must be gifted by God with the spark of the prophet. Such teachings are slightly degrading of the Imperial nobility, and could easily wax anti-institutionalist should the incentive be sufficient.
It is the fear of many orthodox priests that the recent conflicts with the Sector Trade Organization, specifically the mass Exigo of House Vela, will offer motivation to the Masoodite cause. Already, preachers stir in lecture halls and cloisters, with winds of dissent carrying word of a future under the Church and the Church alone.