Clean torstol

Torstol is the highest level herb in the game. Clean Torstol may be combined with five different Extreme potions to create an Overload potion. Also, adding Jangerberries to a torstol potion(unf) creates a Zamorak brew, but this is a less common use for torstol than overload potions. It takes level 75 herblore to clean torstol; cleaning torstol gives 15 herblore experience.

Obtaining
Torstol may be obtained through the farming skill. Planting a Torstol seed in a herb patch requires 85 Farming. Torstol seeds are very rare drops, but nevertheless farming is the most common source of Torstol.

Torstol may also be obtained from the Sinister chest in Yanille's Agility Dungeon. To unlock the chest a player needs a Sinister key, which is a drop from Salarin the Twisted and a possible item of loot from a Magpie impling. Before the release of the farming skill, the Sinister chest was the only way to obtain Torstol.

Torstol may also be obtained as a possible alcove reward from burning Vyre corpses on pyres in the Paterdomus temple's Columbarium.

Torstol is one of the four herbs that cannot be obtained from the Sorceress's Garden minigame in Al Kharid, along with Toadflax, Snapdragon, and Wergali.

Market
Torstol has been maxed out in the Grand Exchange almost all the time ever since the herblore update in October 2009, due to torstol's use in making Overload potions.

As of 8 February 2010, clean torstol has a max price of over 21,000 coins, whereas in September 2009, clean torstol herbs were worth about 3,000 coins each. Torstol seeds have also seen a similar increase in price.

Starting 24 January 2010, clean torstol did crash in price from around 22k to 17k, but since then the price of grimy and clean torstol have fluctuated.

The price of torstol potions(unf) has been rising very slowly, making them appear to be worth less than torstol herbs, even though a torstol herb is used to make the potions. However, it is unknown if torstol potions(unf) will actually rise to the price of torstol herbs because torstol potions(unf) are only used to make Zamorak brews, and it is unclear if these potions have enough demand to be made with torstol herbs worth over 20k each.