It would be a Sect or a denomination. Problem for me is this isn't how it works. There is no over arching Christian religion that owns the property of all the denominations. While they may share several tenanted, and be lump together in a simplified category, they are for all real purposes separate religions. This can already be modelled by having several religions that are in communion with each other, or by using the ranking system to form your own distinct groups within the religion.
Religious schism is I believe already on the to do list. Not sure how they will handle which temples join which faction, or if that has even been decided at this stage. One point to remember, religions are supposed to be mostly about RP. They have got some nifty in game mechanics these days, but still by and large they are a RP construct.
My example may noy be the best, but there are always groups within religions who have a slightly different view. And ones in a while they make a fight and split. sometimes however it is simple a group within the religion who stay there for over decades. I used the name cult because I never heard of denomination and Sect is mostly used bad in dutch media.
