Quote Originally Posted by sapi
So do you believe that it's due to killing both the faction leader and his heir in the same turn. Interesting...my theory is that the game assigns the new heir at the end of the battle, but only after the current heir has taken over. If he's dead, pandemonium ensures :P
Actually I did some 'royal pruning' by sending my Emperor and his heir to their deaths against the rebels of Bern (I had my eyes on it so I wanted to do some honest damage).

I got both of them killed, in fact the heir dies a little before his father in the battle, but that can hardly be an issue.
Afterwards the game played fine with a new emp and heir. Interestingly the heir that died was now added as a dead emperor. Interesting since he died first.
But the main point was that the game still played on.