Wyrmhide Raiment (5e Equipment)

Armor (studded leather), legendary (requires attunement)

Created from the flesh of a greatwyrm and fastened with the smallest slivers of its bones, this light armor confers the dragonslayer a degree of protection few heavier buttresses can match, both in terms of magic and material.

While wearing this armor, you gain a +3 bonus to AC, you have advantage on saving throws against the actions, features, and spells of dragons, and you have immunity to one damage type that is determined by the kind of dragon that provided the leather (see the table).
Additionally, whenever you take damage from a melee attack, the attacker takes 1d10 of the same damage type this armor gives you immunity to. After a creature takes this damage, they have disadvantage on attack rolls against you until the end of the turn.