First some info you need to know when playing with this unusual faction:

1. Although you play as the papacy, you’re not the pope. So you can’t grant catholic factions money (it won’t go from your treasury either), you can’t excommunicate other factions and you can’t ask for crusades against factions.
You are however in control of the papacy which means that you yourself can’t be excommunicated and catholic factions that fight you will be automatically excommunicated. In other words, this is a loophole in the ‘you-can’t-excommunicate-other-factions’-rule. Use this information at your own discretion.

2. You’re faction leader has sworn an oath of celibacy. So how virile he might be, he won’t give you legitimate heirs and princesses. Once your faction leader dies, your best general will take his place.
This spells disaster for your faction as this will drain you of any decent general (kings die of old age generals live until something cold and shiny pierces them). So make the most of those average to good generals you’ll get (by chance or bribe) and let them command as much as you can because they won’t be there for more than a few decades.