Armor of the Warleader (5e Equipment)
From D&D Wiki
Armor (half plate), legendary (requires attunement)
This bronze armor was forged in preparation of a great war and is decorated with straps of toughed leather and dragon scales. A cloak of red cloth flows in the wind behind the armor and a horn made from dragon-bone hangs at its side. While wearing this armor, you have a +1 bonus to your AC, and have resistance to slashing and piercing damage from nonmagical attacks. As an action, you may blow the horn, making all creatures of your choice that can hear you within 120 feet deal additional damage on all damage rolls equal to your Charisma modifier(minimum 1) until the start of your next turn. The armor regains use of this effect at dawn.