When the Prince of Darkness captures the City center of Urr (i.e. the palace of the Captain Regents, the Grand Council Hall and the Ziggurat) before or in turn 13, the game ends immediately. The Prince of Darkness then is the victor and his personal Imperial Guard will occupy the City. Independent of the outcome of the game, his mercenaries and raised undead will leave him after the game.
Having completed two game simulations, we, the designers, do not know what the final outcome will be. This is also by design. When the Prince of Darkness wins, the next megagame within the Urr setting will be called The Uprising of Urr. When the Prince of Darkness does not capture the City, the next game will be The Witches of Urr.
Thus, when this game is played, we hope we will see you another time for a next episode of these epic events.