Wondrous Item, common
This sticky, adhesive fluid ignites when exposed to air. As an action, you can throw this flask up to 30 feet, shattering it on impact. Creatures within 10 feet must make a Dexterity saving throw. On a fail, the target takes 2d6 fire damage and is on fire. Each turn they will take 1d4 fire damage. A creature can end this damage by using its action to make a DC 10 Dexterity check to extinguish the flames.