Alchemist's Firestarter

Common, alchemical, impact, unwieldy

This ammunition features a sealed clay sphere containing a reservoir of alchemist’s fire. When loosed, the bulb shatters on a hit or miss and its contents ignite. On a hit against a creature or object, do not roll normal damage. Instead, the target takes 1d4 fire damage at the start of each of its turns. A creature can end this damage by using its action to make a DC 10 Dexterity check to extinguish the flames.

From Enchanted Ammunition: 101 Alchemical Arrows and Booming Bolts

Notes: Damage: Fire