I'm playing with a custom kingdom and sovereign. I have de betrayers ability and my sovereign recruits champions for free. At some point in the game, I can't recruit champions anymore, as the recruiting cost is in negative gildar. Usually -256 gildar, but sometimes it's another absurd negative amount. In my most recent game, I surrounded the unrecruitable champion with units as to prevent it's recruitment by my enemies, but they recruited it nonetheless. Anyone else has had this problem?
