A tarnished gold band made in image of two dragon wings encircling the finger.

This enchanted ring has 4 charges and it regains 1d4- expended charges daily at dawn.

Whenever you hit an enemy with a melee weapon attack, you may expend 1 charge to force the target to make a DC15 Con saving throw or take 3d6 poison damage.

If the ring ever drops to 0 charges, roll a 4 sided die. On the roll of 1, the ring disintegrates into a cloud of poisonous gas that is 5 feet in diameter. All creatures who enter or start their turn in the cloud are poisoned for 1d4 hours.

Curse

If the creature makes is successful with it's saving throw against this ring's effect; the wearer instead takes 3d6 poison damage.  Once you attune to this ring you cannot remove it unless you are targeted by the remove curse spell.

"Upon reaching the swamp where the Hydra dwelt, Sadako covered her mouth and nose with a cloth to protect herself from the poisonous fumes. And it descended from Heaven with its eyes like akakagachi, it had one body with eight heads and eight tails. It's length extended over eight valleys and eight hills, and if one looked at its belly, it is constantly bloody and inflamed"