One thing that ive already told you, i dont like the way that there's only one entrance to each castle
I agree with Tom. This is going to have one very clear set of strategies with only one entrance. If you move the castles up near the wall, you can then make a 1-way passage through the wall out of the kingdom into the adjacent plains. That would create a more "attack" friendly environment, and also eliminate some of the significance of catching a bad dice streak early in the game.
Alternatively, you can leave the castles where they are, and create a one way attack in through the wall (i.e., breached wall), which will create a more defensive challenge, but at the same time increase lead time to successful attacks because the would be assailant will need to have enough troops to plug two gaps rather than one to avoid being overrun by another player (could be less relevant for 1v1 but would be very interesting for >4 player games.