Nightstalker's Armor of the Northeastern Wind (Patreon)

Armor (plate), rare (requires attunement)

This unusual armor is composed of blue metal plates with a horned helm, and was tempered by the frigid breath of an oni.

Retributive Cold. When you take damage from a creature that is within 5 feet of you while wearing this armor, you can use your reaction to deal 1d6 cold damage to that creature.

Freezing Fog. While wearing this armor, you can use a bonus action to speak its command word to cast the gaseous form spell from it, targeting yourself only, with the following changes:

• You take the form of a frigid cloud of fog, creating illusory frost on objects you touch.
• You can take the Attack action while in this form. When you do, your attacks are unarmed strikes that deal 1d6 cold damage, instead of their normal damage.
• You can use the armor's Retributive Cold property.
• The spell has a duration of 1 minute.

Once this property has been used, it can't be used again until the next dusk.

Mist over mountains,
vicious winds drive frigid air.
Warmth drains from the soul.