Some acts can get you excommunicated by the Pope. This is similar to being an outlaw, with the additional penalty that if you die while excommunicated, your overlord may seize your estates and, in effect, force you to start over in the game with a new, and probably less favorable, position. You should also remember that being excommunicated places your immortal soul in jeopardy of going to Hell. You cannot get a divorce while excommunicated, nor can you marry. You could be excommunicated if you pillaged fiefs held by the Church, for killing a Bishop or annoying an overlord who is on very good terms with the Pope. The Pope can remit the excommunication at any time he believes that the player has sufficiently abased himself and returned to the fold of the Church.