A weapon poison flask is a potion flask originally containing six doses of weapon poison. It is created by using weapon poison on a potion flask.
Weapon Poison can be applied, after which the player will gain the ability to poison an opponent. The poison effect lasts for 2.5 minutes before another dose has to be applied for the poisoning effect to continue and deals between 12-26% of your ability damage per hit.
Poison has 1/6 chance per hit of being applied. This deals poison damage and renews the poison duration. Poison will also hit every 10 seconds and wear off after 3 minutes.
To decant the potion into the flask, one must have at least 6 doses of weapon poison in their inventory, as well as one or more potion flasks. Using the flask on the potion will open a menu to decant them. The optimal inventory setup for decanting potions is 17 4-dose potions and 11 flasks.
Contrary to other potion flasks, all doses of the weapon poison are able to sell on the Grand Exchange. Once the potion has been partially used, no more doses can be added to it. After all six doses have been applied, the flask will shatter and disappear. Flasks can be combined together, but the empty flasks will still be destroyed afterwards.
If the full, 6-dosed version of this potion is consumed, each dose would cost about Expression error: Unexpected < operator. coins.