What about an order of monks who have a duty to perform but have abandoned it to hide from the world? Basically this would be sloth, in the sense of "acedia", the dark side of monasticism.
I don't know much about the Church of the Silver Flame in Eberron, but I was thinking the monks were stewards of an eternal fire but after getting involved in some political conflict they were harshly persecuted. And so today the monks have withdrawn from the world, along with a desperately needed artifact/divine power. Their attitude is "it's going to hell in a handbasket anyway, there's nothing we can do."
Their evil would come into view when they refuse to help/turn over their artifact, turning a blind eye to large scale suffering. It might take a little setting up to do, but it is the 4th sin after all.
