Moonlit Aegis

Armor (shield), rare (requires attunement by a spellcaster)

This magic shield glows softly under moonlight. While you're attuned to it, you know the moonbeam spell, which doesn't count against the number of spells you know or have prepared. It has 5 charges and regains 1d4 + 1 expended charges daily at dusk.

While holding the shield, you can expend 1 of its charges as a reaction when you're hit with a melee attack. When you do, the shield releases a flash of brilliant moonlight. If the attacker can see the shield, the triggering attack roll takes a −1d4 penalty, potentially causing it to miss. Hit or miss, each creature that can see the shield within 5 feet of you (other than you) must then make a DC 15 Constitution saving throw; a shapechanger makes this save with disadvantage. A creature takes 2d8 radiant damage on a failed save, or half as much damage on a successful one. The radiant damage increases to 2d12 if it's between dusk and dawn.

The cleric stood unbothered amidst the raging onslaught. Good rallied against evil: light pitched against the pitched dark. It wasn't frightening, nor was it unfamiliar to them.

In their grasp was the silvered disk of a crescent shield, depicting a glimmer of the sun from behind a curved moon. To the unfaithful, it would show the mighty sun cowering to an unyielding moon. To the cleric—to the knowing—it showed the opposite: how they were one and the same, and how the golden light of the sun was transformed, made cold and sharp, by the silver moon.

The cleric, oft warm and welcoming, turned steely and frightful then. And as evil's steel was brought upon them, ringing against their shield, so too was the unforgiving light of the moon brought to bear against evil in turn.