Casket of Ancient Winters
The Casket is a magical item sacred to the Frost Giants of Jotunheim.
When used, it generates freezing winds. It was originally created as a terraforming device, to make areas habitable by Frost Giants. During Odin's Conquest of the Nine Realms it was repurposed as a weapon.
The casket was taken from the temple in which it was housed by Odin after he defeated the Jotuns in battle. Since then it has been kept in the Odin's Vault.
Since the creation of the Congress of Realms, the Jotuns have repeatedly petitioned to have it returned to them, however the All-Mother has repeatedly refused the request.