Whatever it was, it was strong, ancient, and overbearing. The will didn't do anything but directly exert its intent against any magical construct in the open air. To cast successfully, Jon would have to overpower its intent and overcome the volatile ambient magic at the same time. Even he could not compete with it, and together with the volatile ambient magic, it truly made almost every form of spellcasting impossible. Fire magic somehow slipped around the hostile intent, maybe due to it being based on the manipulation of a certain element or his draconic bloodline. The volatility of ambient magic was in line with the general nature of the fire element. Blood magic was almost impossible to stop or overcome, so it wasn't surprising that it was working. Runic inscriptions required a solid surface to be etched upon, but almost all materials decayed with time one way or another. When not inscribed on a sturdy material, the magic would dissipate if the inscription itself got damaged.