The Shade Isle Campaign
Abbey fanatics are normal humans (half a hit die, +0 Fighting Capability) which have been brainwashed into the Church of Acrefatum. They remain within Shade Abbey for the most part, serving the cult there as a willing slave-labor-force. They tend to wear only rags, as opposed to the cloaks of the full cultists or the robes of the priesthood.
Many abbey fanatics show scars, burns, and other signs of abuse. Most don’t seem particularly well-nourished either. And yet, they’re almost mindlessly loyal to the Church. They’ll attack intruders with a berserk (if pitifully ineffectual) fury, ignoring pain and injury like a drunkard—or a madman.