Bag of Foul Wind
Wondrous item, rare (requires attunement)
This coarse burlap sack is 1 foot in diameter and inflated like a balloon, with the end secured by some twine. As an action, you can undo the twine causing a blast of fetid green fog to emerge. Each creature in a 60-foot cone must make a DC 15 Constitution saving throw. A creature takes 8d8 poison damage on a failed save, or half as much damage on a successful one. Creatures are affected even if they hold their breath or don't need to breathe.
Once you use this item, it becomes deflated and cannot be used. If you retie the end of the sack with the twine, it reinflates after 12 hours and is ready to use again.