MTW: Inquisitors and increasing piety

I was playing with inquisitors last night, trying to discover how to properly use these guys to create dismay and unhappiness in my enemies. I found that if you try to burn a guy enough times and he survives it, they develop a V&V of devout (+2 piety) or born again (+4 or 6, I think). I had one enemy go from 1 piety to 6, after 2-3 inquisitions.

After discovering that inquisitors give V&V bonuses IF they don't burn a guy, I then took a 0 level inquisitor and sicced him on my king (piety 2). He gets two new V&V, devout and secret athiest. I decided to do the same with my heir, and he gets the same thing. (These british kings just aren't very interested in religion, are they?) I think, "Hmmmm, if piety were good for anything, this'd be a great!" I then use the inquisitor on a few of my higher piety generals. They all pass, and get a V&V after the 2nd inquisition I believe (sometimes the first).

Now, if I could only remember what Piety is good for?

With inquisitors, do they cause a zeal balloon? That is, they go in, the zeal goes up a little, then a lot, then drops out? If so, one could set up a crusade, and send in an inquisitor in the enemy provinces. Zeal balloons, you move the inquisitor before it drops, and send in a cardinal or some bishops to keep the zeal high in the province. Then, when the crusade rolls in, everyone runs off and joins.

I wasn't quite remembering exactly how the inquisitor process worked, and with no internet access, couldn't pull up the umpteen guides many people have been kind enough to put in here.

You right on most things: unsuccessful inquisitions can increase the piety of their targets, and inquisitors increase zeal in a province until the point were they start an "inquisition of individual" and begin burning the peasants. Inquisitors also reduce heresy. Inquisitions are less likely to succeed when a bishop or cardinal is present.

Piety in a governor or king increases the zeal of the provinces. High-zeal provinces don't like to be ruled by an impious governor. However, staying in a high-zeal province usually grant your kings/governors extra piety. High zeal facilitates an inquisitor's work, while high piety impedes it. Bishops and cardinals do not increase zeal, BTW, but an Imam does.

However, unsuccessful inquisitions can turn a target away from God, making him an atheist or a heretic. The result of this is lowered piety, making it a gamble whether you will benefit from investigating your own generals. However, persistent persecution of an enemy character will eventually lower his piety, making him more vulnerable to inquisitions.