Hypoletta

The Hypoletta plant is a large, slow-growing bush found on the southern continent of Yanth, near the banks of lakes. It thrives on the mineral deposits found in the otherwise poisonous waters, which also contain a species of gigantic, amphibious insects uniquely adapted to the lethal environment.

The plant's seeds are used to create a potent anaesthesia useful in treating combat injuries. Crushed and treated with the lake water, the gases released are known to double the rate of success for first aid treatment.

Source

 * Dark Heresy (2nd Edition): Enemies Without (RPG), pg. 101