Playing as Milan, minding my own business, quietly expanding, dealing with various greedy neighbours coveting Corsica and Sardinia, and sending the Pope regular back-handers to keep him sweet. We had the College of Cardinals locked down and one of our own installed as Pontiff (and as quite a young man so he would be in there for many hears) and with plenty of high-Piety priests about the place it was going to stay that way for a long time to come.
The only fly in the ointment was that the Papacy had allied itself with Spain, who'd taken up the cudgels against us about the time we finally got Sicily to sit down and shut up. No problem, the odd Papal army wandering about the place was left to do its own thing. Then the Spanish attacked one of our own ships and there was a Papal States fleet adjacent to the pair of us. So he turns up as part of the attacking side and I couldn't even flee the combat.
Moments later the Pope is yelling at me, all my Papal favour has disappeared and I'm excommunicated, and I'm frantically searching for some way to placate him...
The Council assembles and regretfully informs Duke Puccio that he needs to do the decent thing for the good of the State. So our leader bids his tearful family farewell and goes to find a sword to run on. It's a near thing at that as he is quite badass, but eventually he manages to get the enemy to kill him. The Pope, however, is quite unmoved; Milan remains excommunicated and at war with the Papacy.
A little later a Papal army turns up outside Tunis, and Our Man In Rome craves an audience with His Holiness to say, amid the desperate palm-greasing with florins and so on, "Say, why don't we make you a gift of this valuable conquest of ours?". The Pope exclaims with delight "You truly have our best interests at heart! We accept!". So Tunis turns white, our army of occupation is standing on the seashore with their bags packed, we offer a few more routine bribes and then say "How about a ceasefire?".
"Nope".
Over the next few turns we fork over increasing amounts of specie to the permanently-insolvent Church, we build cathedrals, we refrain from attacking our neighbours... and the Papacy turns up outside Algiers and Florence and we're close to rage-quitting the campaign. Fortunately it turns out that the Papacy can't assault for toffee and when the Pope himself tries to solo Naples we see him off with a couple of units of Milanese spears although he doesn't stay on the field long enough to get killed.
Back to Our Man In Rome and we throw bag after bag of florins at the Throne until we finally get our relationship with the Papal States all the way up to "Perfect", and then we offer money, trade rights, map information and yet another region in exchange for a ceasefire and manage to get the proposal all the way up to "Balanced", and this from a 7-influence Diplomat.
"Nope".
Muttering something about a game of soldiers, the Milanese saturate Rome with spies until the gates are guaranteed to be open, and then the former conquerors of Tunis land on the beach along with some reinforcements they picked up in Palermo and rudely barge in to stick the Pope's head on a pike. Just before doing so we inform the Papal States that they can whistle for the thousand-florin-per-turn-for-ten-turns tribute we had promised them, and they exclaim about what an untrustworthy bunch we are, if you please.
In the ensuing Papal elections the Milanese cardinals swamp the voting chamber and a new Milanese Pope replaces the old one, although his new palace will be a rather humbler seat in Tunis and we are having Rome extensively redecorated. And our excommunication has been scrubbed and we are top of the totem pole for now.
Silly Pope.