The Papal Controller is a powerful honor that can be held by only one catholic nation. The country with most cardinals in the curia is the Papal Controller. The Papal Controller will gain a few bonuses including prestige and an additional diplomat.
Gaining Control of the Curia
The seven cardinals who make up the curia cannot be swayed.
There are five cardinals on the outside, waiting to get in to the curia once another Cardinal dies. These cardinals can be swayed by investing papal influence into them. Papal influence can only be spent if it would gain you the most influence with a particular cardinal. This means that if all of the cardinals are heavily influenced by other nations then you may not be able to spend influence. You can also spend papal influence to further strengthen your hold over a cardinal you already influence.
Each cardinal has a country of origin, and that country gets a bonus to influence him.
One of the five candidates is randomly chosen to be invested whenever one of the seven invested cardinals dies.