You could do part puzzle game, part rts. What I mean by rts is that you can give the knight commands but you can’t control him directly. And maybe he doesn’t always do what he’s told, and you have to account for that somehow?
Could make for an interesting roguelike, too, as you try to help this endless stream of knights rescue you.
I’m surprised no one has mentioned eve online yet. Since it has an entirely player driven economy, you end up with thieves and scammers that can steal thousands of man-hours worth of stuff from you and your friends/guild/team