Tralb was a poison that was said to be extractable from either of two sources: snakes found in the Holy Desert of Raraku in Seven Cities; or from certain mushrooms. The name came from the Seven Cities (Bisbrha and Debrahl) language.
Tralb's effect was to leave its victims spasming, writhing, foaming at the mouth and bleeding from the eyes, but still conscious and fully aware of their wretched plight. It did not immediately kill its victims but left them in horrible agony until either their hearts gave out or they died from dehydration (from uncontrollable incontinence) - death being due more often to the latter rather than to the former. The poison was so virulent that any contact with the blood, saliva, or other bodily fluids from a victim was enough to poison another. However, tralb was sometimes given in tiny doses (i.e., "a drop") by healers to stop tremors such as often afflicted the elderly.
It was used by Iskaral Pust, High Priest (or 'Magus') of High House Shadow, to make tralb tea - which he drank and found "warming", but it was not specified how common (or how wise) a practice this was in general.
'Moranth tralb' (presumably from Genabackis) in even the smallest amount in the bloodstream would quickly bring about unconsciousness, which would then lead to a deep coma that usually resulted in death. Larger amounts of this form of tralb guaranteed a speedy death. It was thought by the Darujhistan assassin, Krute of Talient, that the famous assassin Rallick Nom (also of Darujhistan) utilized the more humane 'Moranth tralb' in his work.
Although its place of origin is not specified (unlike for the tralb extracted from snakes), the tralb derived from mushrooms was perhaps the form of the poison known as 'Moranth tralb' - given not only the damp nature of the habitat of the home of the Moranth in Cloud Forest of west central Genabackis, but also the apparent availability of 'Moranth tralb' (at least to assassins) in Darujhistan.