Papal army
A papal army is an army approved by a Diocesan Sergeant.
A papal army has the particularity of being able to change the method of appointing a Bishop when it controls the status quo of a diocese's capital.
Basically, there is no need to do so since, by default, all dioceses are under the authority of the Pope, but if a royal army were to take control of the status quo of a diocese's capital and change the method of appointing the Bishop to benefit the sovereign, then such a papal army would be needed.
If it does so, then it gives back to the Pope the power to choose (through the relevant Episcopal Assembly) the next Bishop at the end of the current Bishop's term of office from the list of potential candidates that can be consulted in the cathedral.
A papal army can also increase the amount of annates if it controls the status quo of the diocese's capital.
The Diocesan Sergeant can see the list of all the papal armies in the diocese.