Ok, sorry for ranting. But let me conclude then. RoP does not describe cathars as "wrong" imho. The authors are rather driven to make all the "real" medieval religions fit into one divine context. This ambition works better with Judaism/Christianity/Islam and it seems even with Zoroastrianism than with the dualistic heresies such as Catharism and Bogomilism because they believe that god who created the world was evil. If the creator of the world had one divine son or not is not as fundamentally dividing as if he was "good" or not. I can fix it with saying that Catharism actually isn't like that in ArM but to me that seems wrong. As God and the Devil (or the Devil and God) can not be one the same playing ground I must fix this somehow or the Divine Realm will collapse. The Holy Seat in Rome just can not project an Aura that is sacred to the Cathars. So my conclusion is that the Cathars basically are right. The world was created by a lesser God and he did not do a very good job. This would explain why there are other powers in the world such as the Infernal, Magic and Faerie. This lesser god might not be as bad as the Devil - I would rather make him the God who speaks in Exodus 20:5 and Deuteronomy 5:9;
"For I, the LORD your God, am a jealous God, visiting the iniquity of the fathers on the children to the third and fourth generations of those who hate Me".
If the Church is his instrument on earth the Albigensian crusade suddenly makes perfect sense. If I was a game creator I might not take this path in order to not offend some potential buyers and indeed this might be within the paradigm of ArM. I would have the creator of the world the "Undergod" and the creator of the spirit the "Overgod". This actually fits well with some theological movements such as gnostisism and Mithraism (if we are to believe Ulansey's The Origins of the Mithraic Mysteries: Cosmology and Salvation in the Ancient World) even if it might not fit with the theology of the average Mythic Europe peasant. The Undergod is jealous of the Overgod though and wants to be more like him/her so he can actually be good at times to and have the angels covering up for him (and not telling anyone the truth about this matter if they happened to know it). It is not really clear what "the son of Man"/Jesus(or Mithras)-figure is as both the Cathars and the Christians believe him to be good but I don't have to explain that in order for the world to work. I will not explain this to my players but they will notice that the Undergod (disguised as LORD, your God) actually is against the Cathars even though they actually are better people than most. The Overgod is unable/unwilling to save the Perfecti because there is no point in making their souls stay in an imperfect realm. Their powers will make them see and save their souls but will not help them otherwise. To the players Mythic Europe will work just as before but with an ugly inkling of that something just isn't right about the world...