Auras

Auras and Magic
All souls are inherently magical and radiate that magic around them. The Aura of a soul can be manipulated and changed without affecting the soul it's bound to, but they are intrinsically attached and are, in essence, one. Powerful Auras interact with the magic around them, which is what results in a mortal who can wield magic.

Individuals who cannot wield magic cannot do so because the conduits in their bodies are 'turned off', and thus, no magic seeps out of them to interact with the world around them.