There is a veil which separates our reality from a parallel dimension that contains Eldritch abominations. An ancient empire has discovered that they can harness the power of this realm by summoning demons across the barrier. This is done through the use of human sacrifices. The more powerful the demon, the more sacrifices are needed.
A religion has formed with two separate modes of thought. One sect believes that these demons are tools to be exploited for humanity's purposes. This focuses on enslaving demons as weapons, using them for their powers and as servants. The other sees them as transcendent life forms to be worshipped and held sacred. By combining themselves with demons to create demon hosts, humans can shuck their mortal shells and ascend to a higher state of being.
Looking through historical records, it seems that religions often break into various sects for simple theological reasons that seem silly, at least to outsiders. These can lead to schisms that fracture the faith forever, and can end in civil wars. I need a way to maintain this religions coherence with these two ideologies to keep the empire stable.
We are supposed to learn from the past to avoid repeating its mistakes. How can I design this religion from the ground up to maintain its stability?