You still have to set up Y to define "we".
Unless you do it at the level of the realm; but in that case you do it with the secular tools at your disposal. You don't need to found a religion to arrest and ban priests.
but the thing is.. you can't round up peasants who believe in evil things and kill the lot of them. you can't even get the priests unless you are a follower.
the "we" would be anything but X.. but most typically a religion so minor that it doesn't get founded officially in the game.. i guess part of the pagan stuff.
