From the back of the box:

The players are Charlemagne's heirs - hence in constant conflict with each other. Here he has asked them to build castles in some of his favourite territories. But to do this they must seek and then maintain for as long as possible the support of the five owerful clans of nobles, the paladins (represented by coloured cubes) who administer the Emperor's lands. But then the players on their side can dispose of exceptional tactical resources. One is that they decide themselves the order in which they move. Another , that they can determine how far the Emperor travels, which is crucial, since castles can only be built in his presence. ANd when castles are built in neighbouring territories, these territories can be joined, so that, as the game progresses, great domains are formed, defended by four, five and more castles... In the end, to win the game and gain the emperor's favour - and perhaps even the right of succession - a player must have built 10 castles.