Runepowder Vial is a Consumable(Grenade) item that can be thrown using the Throw action.
Runepowder was said to be invented by Gaerdal Ironhand, the protector god of gnomes. A mere 23 vials were needed to repel an assault led by Kurtulmak and his Kobold Delvers.
Properties
Grenades
Single Use
Rarity: Rare
Weight: 0.2 kg / 0.4 lb
Price: 50 gp 
UID
UNI_UND_Runepowder_Vial
Effect
- When ignited by a source of fire, the vial explodes and deals 5d4+18
Force damage.
AoE: 1 m / 3 ft (Radius) (Need Confirmation)- Saving Throw needs confirmation
Where to find
Obtained from Philomeen in Grymforge during quest Find the Explosives