"Colossus" mentions Ylourgne as a ruined fort up the Isoile watershed, presumably eradicated so that Vyones could arise down river. Twelfth-century Vyones, from "Maker of Gargoyles", could boast "two nunneries and a monastery". As a somewhat worldly city, soon to have a cathedral as well, those sites will be Benedictine. But at the same time, emerged a fundamentalist movement within the Benedictine order itself. This movement started at Cîteaux in 1098, with the founding of the Benedictine abbey there; it really got going under Bernard of Clairvaux in the 1110s. This movement came to be termed Cistercian after the Latin name for Cîteaux.

It occurs to me that the stricter Benedictines in Vyones would have moved up river, where nobody else wanted to live, soon after the events in "Gargoyles". By 1275-81, when "Colossus" starts, the Cistercian discipline up there seems already to have slacked off a bit, given that monk Théophile is not cured of the vices of gluttony and sloth.