After all that fuss raised about the excommunication, I shall throw my in
The excommunication is, in general, a bad thing. Question: how bad? Answer: it depends. When you have a strong, influential ruler and a well garrisoned kingdom with low zeal factors, then excommunication is merely a nuisance - loyalty of your forces and provinces may suffer a little drop, but it won't be enough to start any rebellions or (worse) a civil war. And should they actually do happen, they shall be weak enough to provide just a practice for some of your lower-ranking officers. This is particularly true for the factions that aren't going to launch Crusades (like Poles and Danes), since excommunication has no effect on them.
However, if your realm is feeble, or if you want to launch Crusades (or fulfill GAs connected with the Holy Land area), things get quite bleak. The biggest threat for the excommunicated is that the remaining Catholic factions are free to rush on you (in every second game I play, the excommunicated tend to have others gang up on them). If your armies cannot stand up to the task of defending your borders, such a gang-up may result in a quick and painful game-over. Keep a close eye on the loyalties, too. The more pious generals and the more zealous provinces you have, the bigger impact an excomm is going to take. The pious generals will turn their back on you almost at an instant, and a wave of religious unrest may roll across your territory. At this point, a civil war is likely. Having all your neighbours knocking on your castle gates plus the disheartened populace at your throat... well, it ain't nice at all. Some brave souls would definitely survive such a dire strait, but it would take a skillful and coldblooded ruler to do so.
Furthermore, while you are excommunicated (or at war with the Papacy), forget about Crusades. The Pope will disband your existing ones and won't let you train new ones. Bearing in mind that almost all early GAs other than Conquest and Homelands are Crusades to the Holy Land area, you are banned from a fine chunk of GA points. Expect other Catholic factions (especially those not bent on eradicating you at the moment) to make good use of your handicap in this regard.
So, what can you do about it? There are several ways.
The first and the easiest: make your ruler die You can use Assassins, Grand Inquisitors (later in the game, though) or just send him on a suicide mission. The excommunication is person-based, not realm-based, so once your not-so-pious fatso kicks the bucket, his heir joins the Church again
The second one, a bit harder (depends on how far your armies can reach at the moment) is to make short work of the Pope. The Papacy is just like the American administration - decisions of previous one not necessarily carry over to the next one (All USA citizens please forgive me this shameless pun ) Once you punish the pesky excuse of a priest for scribbling rubbish parchments , you can say hello to the new Pope, and the Church. If you can't reach him with his armies, use agents (high Valour Assassins work well).
The last, and the most difficult one, is to get rid of the Papacy altogether. Unfortunately, this last option is in no way permanent. You can conquer the Papacy and eliminate it as a faction (which also renders all excommunications null and void), but the Papacy, unlike any other faction, reappears even when you have a 200% Loyalty in Rome and Papal States - and every 20-30 years! If you want to keep them down, conquer Rome and Papal states, raze them to the ground (leaving BF and nothing else) and make skeleton garrisons of peasants. Then put a strong army on hold in Tuscany or Naples (enabling you to strike at will into Rome or Papal States). The Pope will reappear with rabble units (reappearing army composition is based on what you have in the province and what tech buildings are present). On reappearance, enter , blast , then withdraw Wait until another time... lather, rinse, repeat as needed.
The Papacy is by far the most annoying faction present. I hope my prolonged treatise will make it more tolerable to all players
Down with the Pope!
(DISCLAIMER: in MTW only )