Black Dragon Oil
Potion, very rare
The viscous green-black oil within this magical ceramic pot bubbles slightly. The pot’s stone stopper is sealed with greasy, dark wax. The pot contains 5 ounces of pure black dragon essence, obtained by slowly boiling the dragon in its own acidic secretions. You may use an action to apply 1 ounce of the oil to a weapon or single piece of ammunition. The next attack made with that item deals an extra 2d8 acid damage. Creatures who take the acid damage must succeed a DC 14 Constitution saving throw or be burned for an additional 2d8 acid damage at the beginning of their next turn.