To highlight Elsbeths point between heathen and heretic: a dominant belief among the Brutor clans, and indeed many clans of the other tribes, is that the Amarr god is just another spirit in a universe of spirits, functionally no different than say Pator, or the old mother. We do not hold that this spirit is specifically the main spirit of anything, only that its goals are to corrupt all and jealously horde as much as it can.
The legend goes that this spirit and those that is has corrupted once attempted to corrupt and claim the Matari people, but failed. In their failure they fled and found the Amarr.