Sole Defender of the Faith

From EU3 Wiki

Any country may claim this title for their particular religion. The claim costs 1000 ducats, but gives you a casus belli on all other countries declaring war on a country with your religion (which you defend), a prestige bonus, a bonus to your armies morale, reduced war exhaustion and no badboy points for a declaration of war supporting an ally with your religion. You will however lose the title as soon as you lose a war. A white peace as the aggressor counts as a loss. There are also some disadvantages being the Defender of the Faith; your trade and production technologies become 20% more expensive and the revolt risk in non-state religion provinces will be higher.

Note: In Europa Universalis III version 1.1, this function contains a bug which never releases the title once claimed. It's fixed in 1.3.