Cragspur promises a bit of a fight, so before heading there you should make sure that at least the Warriors you’re sending on the attack are upwards of a 40% Link rating. Higher is naturally better, but don’t push too high or you’re going to wind up outpacing any new recruits you get here. Take your time, recruit new troops where you can, gather your forces, and make ready. Once you have a good set of six gathered in Terrera (I strongly recommend Prinplup for your main character, and if you have him, bring along Yoshihiro), move over to Cragspur and head out on the attack!
When you move to initiate battle in Cragspur, Oichi pops up as per usual, with a warning that the Warriors there mostly use Rock-type pokemon, so Water, Grass, and Fighting attacks are going to give you an advantage. She also warns you that Fire and Bug type pokemon aren’t going to be of much help, and Normal attacks aren’t going to do much.
On your arrival in Cragspur, you are greeted by Ujiyasu, who notes that you’re the one who’s been gaining control in the Western part of Ransei- and half of the region is already yours. He then warns you that excessive ambition can hurt you, to which Oichi responds that it isn’t about ambition. Ujiyasu’s lieutenant, Kai, pretty much tells her to shut up and stop giving excuses. Ujiyasu, apparently, is a busy man and thus wants to get things over with and out of the way.
When you enter the battlefield, Ujiyasu speaks again, telling you that he is fighting to protect something. Because of this, he will bring his full might to bear against you.
Thus, the battle opens. Cragspur’s field is a massive area composed entirely of rock. Boulders litter the field in a rather threatening manner, atop all three visible slopes. Your field forces will start in a small cut-off area at the lowest point, blocked off from entry to the rest of the battlefield by three gray stones. However, in the pit with you is a button. Once a pokemon stands on the button, the gray stones- Stone Doors- will sink into the ground, letting you escape the trap that you’ve started in.
This clearly is a trap, for the boulders are all set on slopes- and when struck in any fashion, they immediately roll downhill as far as they can before striking a wall! The rocks will damage any pokemon they hit, but in a turn of good luck, the damage is Rock-typed, so anything you brought which resists Rock will also resist the damage from the boulders.