Helm of the Justicars

Wondrous item, legendary (requires attunement)

This helm once belonged to Grand Mage-Arbiter Elodie Scolian, the preeminent leader of the surviving Justicar order. Designed to eliminate the threat that all mages pose to the nonmagical populace, the wearer of this helmet has an uncanny resilience against spells of all kinds. While wearing this helmet, you gain a +1 bonus to AC, you have advantage on saving throws against spells and other magical effects, and spell attacks have disadvantage against you.

In addition, the helm has 12 charges and regains all charges daily at dawn. Whenever you're affected by a spell while wearing this helmet, you can use your reaction to learn the level of the spell and expend any number of charges from the helm (minimum 1 charge). If the number of charges is equal to or greater than the level of the triggering spell, you are unaffected by it. A cantrip is considered to be a 1st-level spell for the purposes of this property.

There is no joy to the life of a Justicar. For as much as we fight, what we fight creeps back to fill in the voids we cannot suppress. For what we can suppress, what we suppress simply hides in the cracks we cannot see. For all we see, what we can see will convince itself our eyes are blind.

We tried to convince them that magic was weak, was heretical, was wrong. But they lived by the evidence of their faulted eyes, seeing only what they wished to of their profane ability. And in this, they could find their misplaced conviction, find the resilience to blind themselves to the truth.

That way was wrong. We could never convince them of their own fall.

Instead, we must convince them of this: moral or amoral, their magic is nothing before us.

—Ultimatum of Purpose, Grand Mage-Arbiter Elodie Scolian