Arsonist's Oil

As a Bonus Action, a creature covers one their melee or ranged weapon with this coating which lasts for 1 minute.

Any creatures hit with a melee weapon or ammunition from a ranged weapon with this coating are striped of their Resistance to Fire Damage for the next 10 turns. Targets that have Immunity to Fire Damage are unaffected.

The bulbous bottle holds a green and brown sludgy - devoid of any suggestion of the threat it carries.

Notes: Debuff, Combat Potion