Religious Much?

Pope Gregory VII excommunicating Holy Roman Emperor Henry IVhttp://www.ssqq.com/travel/rhine2015germanhistory03.htm

   

With all that we know about the political maneuverings of the Medieval Church, it's easy to overlook the fact that the vast majority of people in the Middle Ages were truly devout Christians.  Tithing was widely practiced, with the commoners willing to put in time working on church lands to pay their portions.  The Crusades weren't just a land-grab.  While we may look back on this period in history with cynicism, it is important to remember that the Church wielded immense power, based entirely on devotion of the faithful.
    Priests were the learned men who spoke down from the high places, who spent their lives in seclusion, prayer and devotion, who were guides along the path to righteousness.  Priests also served as educators, tutoring both rich and poor, quite naturally using religious texts to sharpen the minds of their charges.  While some who joined the ranks of the clergy may have been younger sons of nobles, looking for an alternate route to power, the majority of the priesthood had very little to do with political wranglings.
    History texts tend to highlight the conflicts between church and state, jockeying for temporal power, whether it be land or taxes.  However, when the state petitioned church leaders to have their congregations pray for the war effort, they were not simply seeking to sway popular opinion.  They were seeking to sway God.  To them, it was another front.  Yeah, Bob Dylan has a couple questions about having God on your side, but it doesn't mean that folks didn't believe in it.  During this time, the Church accumulated vast amounts of property from those looking to make up for a life's worth of sinning.  You don't put the Church in your will if you're not at least a little concerned about the afterlife.
    Excommunication was the ultimate power of the Church, used to bring kings to heel (as well as others).  A person who has been excommunicated may not take part in the sacraments (most importantly communion) and may be denied contact with any of the faithful (shunning).  Additionally, excommunicated individuals may not perform any of their sacred offices.  Furthermore, many proclamations of excommunication were terrible curses called down upon the transgressor for their misdeeds.  Returning to the bosom of Mother Church required significant, and often public, amends.
    It would be simple to view priests and congregants alike as simple men who desired nothing but power and riches.  However, truth is often far from simple.  The entirety of the Church's power stemmed from the faith of the masses.  While many lords actively opposed the secular arm of the Church, they would rarely oppose the sacred.  More often, they would court the spiritual power of the Church, hoping to turn the power of God to their advantage.  "The divine right of kings" was both praise to the victorious in the struggle for power and damnation to the losers.
   
As far as how to utilize this information in a Fantasy setting, look again at GRRM.  His world has a variety of faiths.  Examine the faithful and their actions.  Much of what they do seems incomprehensible to an unbeliever, but would probably seem inevitable to a member of the faithful.  True faith is a powerful thing.  It is easy to forget this in a modern world founded on "proof".  In a world that lacks our scientific foundations, devoting your heart and soul to the unexplainable seems like much less of a leap.  Allow your characters to show their faith.
   


excommmunication history - http://www.ccel.org/ccel/schaff/hcc4.i.viii.ii.html
anathema - http://chicagounbound.uchicago.edu/cgi/viewcontent.cgi?article=9209&context=journal_articles