[As soon as the command came, she moved forward with an easy, almost casual gate. Upon entering the opposing piece's square, she brought her sword up in front of her and uttered an incantation. Suddenly, what had been so difficult almost seemed deceptively easy. It was like the rules of this dream 'allowed' what happened next.

A spear of earth shot up from the tile beneath the knight, sending it toppling to the ground, shattering as it struck. She watched the rock descend into the tile again and picked up the second sword before sending it skittering to Doug with a wink.]

I suspect that the pieces are designed to be defeated this way. Likely magic. We might be able to fight them ourselves, but 'taking' will work without fail.