The Pope is the religious judiciary of the Catholic Church in Medieval II: Total War. The position can be occupied by any Catholic Priest but only if the College of Cardinals is empty. The pope will then become the leader of the Papal States, and a general. The pope may then call crusades and give missions to factions. He can excommunicate a faction if the said faction falls out of his favor with him, giving other Catholic factions an excuse to wage war on the excommunicated faction. The Pope can call Crusades not only to reclaim the Holy Lands from other faiths, but also to punish excommunicated factions or regions with high levels of heresy. He can be used as a political tool by having one of your own bishops elected pope, thus increasing your favor with him and reducing the favor of his opponents in the election.
Favor with the Pope can be earned in a number of ways: building churches, participating in Crusades, converting regions to the Catholic faith, completing his missions or having your Cardinal elected Pope. Favor can be lost by: destroying churches, having high levels of heresy or foreign religions, not participating in Crusades or not completing missions granted by the Pope.
The Pope can be removed only by his death. He can be killed in battle, assassinated or die naturally. When this happens a Papal Election is declared the next turn.