Green Chromatic Rose
Wondrous Item, rare
While this rose is held, it issues green gas as a harmless visual effect.
While holding the rose by its stem, you gain resistance to poison damage. If you would take more than 10 poison damage from a single source (after applying the resistance), the rose disintegrates, and you take no damage instead.
As an action, you can blow the petals from the rose to produce a 20-foot cone of poison. Each creature in the cone must make a DC 15 Constitution saving throw, taking 3d10 poison damage on a failed save, or half as much damage on a successful one. Using this property destroys the rose.
Source: The Wild Beyond the Witchlight p. 208