FAQ for Dos Rios: Valley of Two Rivers™
If I move one of my campesinos through a space with an opponent’s casa (I know that I can’t stop there), can I build a dam in that space “on my way through?”
A campesino can pass through a space with an opponent's Casa, but he cannot stop there. He can't even pause long enough to build a dam before the people living in the Casa chase him off. So, you CANNOT build a dam with a worker that is on a hex with an opponent's Casa. If you want to build a dam on the edge of a hex with a Casa, you will have to place a worker on one of the neighboring hexes. Yes, this does mean that if you build two Casa next to each other, no other player will ever be able to build a dam between your two "houses."
Can I “chase off” another player’s campesinos if they are in a space with a Casa?
You cannot even ENTER a hex that has both a Casa and a campesino in it. Since you can't even inter the space, you can't possibly attack the campesino there, even if you come from higher ground or with greater numbers.