White Dragon Mask

From Rise of Tiamat: Online Supplement, page 4.

Description
Wondrous item, legendary (requires attunement).

This gleaming mask is white with highlights of pale blue and is topped by a spined crest. The mask reshapes to fit a wearer attuned to it. While you are wearing the mask and attuned to it, you can access the following properties.

Damage Absorption. You have resistance against cold damage. If you already have resistance to cold damage from another source, you instead have immunity to cold damage. If you already have immunity to cold damage from another source, whenever you are subjected to cold damage, you take none of that damage and regain a number of hit points equal to half the damage dealt of that type.

Draconic Majesty. While you are wearing no armor, you can add your Charisma bonus to your Armor Class.

Dragon Breath. If you have a breath weapon that requires rest to recharge, it gains a recharge of 6.

Dragon Sight. You gain darkvision with a radius of 60 feet, or an additional 60 feet of darkvision if you already have that sense. Once per day, you can gain blindsight out to a range of 30 feet for 5 minutes.

Dragon Tongue. You can speak and understand Draconic. You also have advantage on any Charisma check you make against white dragons.

Legendary Resistance (1/day). If you fail a saving throw, you can choose to succeed instead.

Winter's Fury. While your current hit points are equal to or less than half your hit point maximum, you deal an extra 1d8 cold damage with your melee attacks.