A herb is an unidentified primary ingredient used in the Herblaw skill that must be identified prior to being used in a potion. At level 75 Herblaw, players can identify this herb to produce a torstol herb. This awards the player with 15 Herblaw experience.
The only way to obtain this herb is through the Sinister chest in the Yanille Agility Dungeon. However, a player must obtain a key to open the chest by killing the dark mage Salarin the Twisted, by weakening and killing him with strike spells. Also note, obtaining this herb from scratch (without trading) requires 67 Agility to reach Salarin.