This chapter seems to argue in favor of a specific molecule or fundamental piece of matter that causes interaction at a distance (I would probably call it a "Magicule" because I like that name in most books and Manga I've read).
Also, you could make some gnarly-ass caltrops with that earth magic, I would think; making a pointy shape will take control, but they only need to be 8-10 inches, maybe a Foot at best; call it 20-30cm, for best effect.
Kinda cool chapter; I'm glad some other noble didn't show up, and I hope there're no shenanigans or malarkey on their way to chat with the Duke.