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
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 (
Dexterity saving throw, DC 12, to halve).
AoE: ~8 m / ~25 ft (Radius) (Much larger than indicated in-game)- Creatures caught in the blast are knocked back (no Saving throw)
Where to find
Obtained from Philomeen in Grymforge during quest Find the Explosives