The tranquiliser known as Moonflower is a dried moss which grows only on leaves in the Laurelorn forest. Elves use Moonflower to treat Black Plague, for which is quite effective, but otherwise it has no effect on their species. Other races can inhale vapours from boiling the moss and fall unconscious or otherwise become fatigued. Moonflower is used by the most expensive Physicians as an anesthetic.[1a][1b]
Warhammer Wiki