Alchemist’s Fire

This cracked and pitted iron flask has an image of flames etched on it. 

This sticky, adhesive fluid ignites when exposed to air. As an action, you can throw this flask up to 20ft, shattering it on impact. Make a ranged attack agains a creature or object, treating the Alchemist’s Fire as an improvised weapon. On a hit, the target takes 1d4 fire damage at the start of each of its turns. The creature can end this damage by using its action to make a DC 10 Dexterity check to extinguish the flames.