One of the causes of the collapse of the Third Imperium is surprisingly also one of the reasons it lingered on longer than it should have. The Holy Imperium Church was under the governance of the supreme patriarch Callidus Magna. It was he that gave the tacit approval to the nobility for the assassination of the politically impotent Inertis, and then stood in the way of law and order being reestablished so that the authority of the Church rose as the secular rules began to crumble. While the corruption of Callidus Magna caused the spiritual role of the Church as a moral compass to falter over time it nonetheless kept the priests and bishops in power for many decades to come.
Callidus Magna was less and less a public figure as the various portions of the realm fell away to revolution and invasion. Oddly though his power seemed to grow even beyond the mortal lifespan of any mere human. To this day the lands directly owned by the Holy Imperium Church owe their allegiance to Callidus. These lands lie throughout the Forkanzan peninsula. Those lands outside of Forkanza that the Church owned were long ago taken over by groups that had splintered off of the main Church, such as the Church of Fanolania. And as the Forkanzan bishops became more and more enmeshed in local politics and the civil wars between the city states that arose from the ashes of the Third Imperium the clerics and priests found that their own religious and spiritual powers were being relentlessly diminished. It is said that they are no better than rogues and warriors in a scrap.
What role if any Callidus Magna as patriarch played in how the Holy Imperium Church currently operates is a matter of scholastic speculation. What is known for a fact though is that the last patriarch of the great church decreed that only he could name a successor. Thusly left without another option the various bishops and archbishops have continued to carry on for the most part as though nothing has happened. There have been a handful of occasions over the last millennia when one or another of the archbishops has tried to ascend to the throne of the patriarch only to find themselves inexplicably stopped and in the most unnaturally disturbing ways. Whispers of divine intervention to maintain the power of a long unseen and nearly forgotten patriarch continue to thrive among the ranks of the clergy both in and outside of the Church in Forkanza. Sages quietly have been known to suggest that should the Imperium be reformed the old patriarch will be reintroduced as the supreme religious authority throughout the realm.