RuneScape Classic Wiki
RuneScape Classic Wiki
The main RuneScape Wiki has an article on: Weapon poison
The Old School RuneScape Wiki also has an article on Weapon poison.

Weapon poison is a potion that can be made with the Herblaw skill. It requires level 60 Herblaw to make and gives 137.5 experience. This potion is not consumed directly by the player, but is instead used on some weapons in the player's inventory. Only certain types of weapons may be poisoned: daggers, arrows, crossbow bolts, spears, throwing knives, and throwing darts, turning them into their poisoned equivalent. The poisoned weapon is capable of doing additional damage to an enemy slowly over a period of time.

To make a weapon poison, first add kwuarm to a vial of water, then mix in ground blue dragon scale with the unfinished potion.

A weapon poison is also a possible reward from the Observatory Quest.

Unlike most potions, weapon poison has only 1 dose. When applied, it will poison:

Weapon/Ammo Tiers Poisonable
1 Dagger Bronze - Rune
1 Spear Bronze - Rune*
1 Throwing Knife Bronze - Rune
5 Arrows Bronze - Rune*
5 Bolts Bolts, not oyster pearl bolts
6 Throwing Darts Bronze - Rune*

* Black weapon variant doesn't exist in RuneScape Classic.

Dropped by

Monster Combat level Quantity Rarity
Shadow Warrior 64 1 3Uncommon