If you want a mentor, just ask someone. Most of them agreed to be one anyway. Haha. 

Rind was already without a weapon, yes? If so,t he bag can be his weapon and stuff. You can make a cool storyline out of him first finding bigger bags to hold more metal, before something happens and the metal somehow meshes with his body(for instance him becoming part metal), and he doesn't need a bag anymore. 

This is similar to my character, Derik, whose body was experimented on and made into living chains, so his body is his weapons. His magic is electricity and magnetism.