Resonance or a bell represents the peak of true magic, its the Ultimate expression of a arcanists connection to Lumens inherent True Magic and their soul.
A person achieves resonmance by becojming so attuned with the worlds song they began to alter the fundamental frequency or magical essence of lumen, Resonance is not only tied to the users magic but the strength and clarity of their soul.
Once awakened a resonance ability remains unchanging, tis form and core function are fixed upon itsactivation, reflecting the nature of the soul that birthed it. This power is intrinsic and can not be easily altered or removed, making each resonance a unique and permanent piece of a character.
Resonance abilities are highly personal as they reflect the users soul, While being strong they are a limited power, offering powerful but short burst of impact. They require immense focus and internal ability, they often have costs an example is Akiras bell that costs life force to burst the heads of foes. The cost scales off the strength of the target.