Remorhaz Cloak (Patreon)

Wondrous item, very rare (requires attunement)

This cloak is made using a strip of a remorhaz's winglike fins and is lightly reinforced with plates of its spined carapace. The first time you attune to this item, and then again each day at dawn, you can choose either cold or fire damage: you gain resistance to that damage type until you make the choice again.

Fiery Carapace. While wearing the cloak, you can use an action to immediately gain 20 temporary hit points, which last for 1 hour. While you have these temporary hit points, any creature within 5 feet of you that hits you with a weapon attack automatically takes 2d6 fire damage, as flames erupt from your wounds. If a creature reduces these temporary hit points to 0, a wave of fire explodes from the cloak. Each creature within 10 feet of you, other than you, takes 2d6 fire damage from the explosion. Once this property has been used, it can't be used again until the next dawn.

Boiling Blood. If you're a barbarian and are wearing this cloak, your blood boils whenever you rage. While you don't have the temporary hit points from the cloak's Fiery Carapace property, any creature within 5 feet of you automatically takes 1d4 fire damage whenever it hits you with a weapon attack while you're raging.

"So when it's cold, it keeps you warm. When it's hot, it keeps you cold. When your enemies attack, it melts them back."
—Ancestral Lizard displaying their prize