Source: Bigby Presents - Glory of the Giants

Wondrous Item, Very Rare (Requires Attunement)

This thick, fur-lined cloak has the frost rune stitched on the hem in silvery blue thread. Frigid wind swirls around the cloak, regardless of the weather.

While wearing this cloak, you have resistance to cold damage. Additionally, when you move within 5 feet of a creature, you can cause the cloak’s cold wind to buffet the creature. The creature must succeed on a DC 14 Dexterity saving throw or take 1d6 cold damage and have the prone condition. A creature can be affected by the mantle only once during a turn.

Invoking the Rune. As an action, you can invoke the mantle’s rune to cast the Sleet Storm spell (save DC 14) with it. When you use the mantle to cast the spell, the area of the spell isn’t difficult terrain for you, and you can see through the storm, ignoring the normal penalties of a heavily obscured area.

Once the rune has been invoked, it can’t be invoked again until the next dawn.