This urn is chipped from a single chunk of obsidian. It has a tightly fitting lid, weighs 4 pounds, and holds up to 1 gallon. It can contain any material or liquid no matter how hot, without cracking or even heating up, so long as it is sealed within the urn.
The urn has 5 charges and regains all expended charges each day at dawn, or 1 charge each hour it is filled with molten lava.
While you are attuned with the urn you are resistant to fire damage.
Additionally, when you speak the command word and expend a number of charges the urn begins to glow with a bright red light in the facets across its surface for the next minute.
For the duration you are immune to fire damage and any creature that ends its turn within 5 feet of the urn must make a Dexterity saving throw (DC 15). The creature takes 2d6 fire damage on a failed save, or half as much damage on a successful one. This damage increases by 1d6 for every charge expended above 1.
If you thrust the urn at a creature as an attack action that creature must make a saving throw or take damage as above. If you are able to make multiple attacks this replaces one of them.