soulfire constructs

"Well..." Bob said, "yes. And no. Hellfire is something you use to destroy things. Soulfire is used the opposite way-to create stuff. Look, basically what you do is, you take a portion of your soul and you use it as a matrix for your magic."
I blinked. "What?"
"It's sort of like using rebar inside concrete," Bob said. "You put a matrix of rebar in, then pour concrete around it, and the strength of the entire thing together is a great deal higher than either one would be separately. You could do things that way that you could never do with either the rebar or the concrete alone."
"But I'm doing that with my soul?" I demanded.
"Oh, come on, Harry. All you mortals get all hung up over your precious souls. You've never seen your soul, never touched it, never done anything with it. What's all the to-do?"
"So what you're saying is that this hand construct was made out of my soul," I said.
"Your soul and your magic fused together, yeah," Bob said. "Your soul converted into energy. Soulfire. In this case, the spirit energy drawn from your aura right around your right hand, because it fit the construct so well, it being a big version of your right hand and all. Your standard force-projection spell formed around the matrix of soulfire, and what had been an instantaneous exertion of force became a long-term entity capable of manipulation and exertion to the same degree. Not really more powerful than just the force spell, as much as it was more than simply the force spell.”


Small Favor Chapter 46, Page 416-417