Hemlock
Description
The Hemlock Plant appears relatively harmless, featuring long green stems with small white flower buds at the end. At a glance it looks very ordinary and could be mistaken for other plants with a similar appearance. However, if consumed the chemicals contained within attack the central nervous system, numbing and weakening the consumer. A high enough dose will inhibit the creature's respiratory system, eventually causing them to die from suffocation. Very little of this plant need be consumed to have a powerful effect on an average sized humanoid.
Lore
Hemlock has been used throughout history as an assassination tool, with small amounts being placed in a subjects food at regular intervals. By the end of the day at the latest, the subject is dead, and the killer walks away without anyone the wiser to their methods. One can prepare the toxin by extracting the plant's juices, or simply feed it raw to a subject. The ease of use and common growth of the plant has made it very difficult to control over the years, although it is highly illegal in most societies.