Verdant Fang

You can attune to this item only if you’re in the good graces of the green dragon who granted it to you. You attune to the fang by pressing it into your mouth, whereupon it replaces one of your canine teeth. While attuned to the fang, you can speak and understand Draconic, and you can use an action to breathe a 15-foot cone of poison gas. Creatures in the area must make a DC 12 Constitution saving throw , taking 4d6 poison damage on a failed save or half the damage on a success. You can’t use this property again until you finish a long rest .

As an action, you can bite down on the fang, destroying it. Doing so sends a mental distress signal to the dragon who granted you the fang; the dragon immediately learns where you are and will come to your aid.