People the species "Stringborn" possess the unique ability to harness the vibrations of these ethereal strings. They can this with their hands, if experienced, or do this through catalysts, which could be any object. These catalysts serve as bridges between the wielders and the strings, allowing them to manipulate physical concepts/items, e.g. gravity, a chair, mass, etc. Hubinki uses this to leave an attack somewhere, and if someone walks into it, they get hurt.. His catalyst is a brass knuckle