Arsonist's Oil is a Consumable(Coating). It can be applied to a weapon to give it special properties for ten turns.
'It was then that Swires tossed the oil. It splattered the cambion, and all at once its skin of brilliant carmine dulled to dark, a red like cheap wine, and the fiend vented this sound of anguish I almost pitied, for its very affinity to fire was now undone.'
Properties
Single Use
Rarity: Uncommon
Weight: 0.1 kg / 0.2 lb
Price: 25 gp 
UID
ALCH_Soultion_Oil_RemoveResistanceFireUUID
bd118cc0-eb90-412d-8229-6749f42df5c6
Effect
- Coat your active weapon in Arsonist's Oil.
Condition: Coated in Arsonist's Oil
Duration: 10 turns
- Targets with Resistance to
Fire damage become Vulnerable to it instead. - Targets with Immunity are unaffected.
Condition: Arsonist's Oil
Where to find
- Crafted via Alchemy by combining
Sublimate of Frosted Ears (procured from 
Frosted Ear) and any Ashes
Notes
- This coating can be used by wild shapes but it does nothing on attack.
- The description seems to be misleading because Arsonist's Oil does not replace fire resistance with fire vulnerability, it simply adds fire vulnerability. You can still achieve fire vulnerability by applying Arsonist's Oil on targets which have 1 turn of
left and no native fire resistance. - One of several references to the gnome adventurer Lupperdiddle Swires. Others appear in the descriptions of the Potion of Glorious Vaulting, the Swiresy Shoes and Swires' Sledboard. "Swires" is a reference to the Discworld books.
