The strangler is a rare poison, which makes the person unable to breathe. The poison is made from plants that are only found on islands in the Jade Sea. The leaves of the plant are picked and aged, then soaked in a wash of limes, sugar water and rare spices from the Summer Islands. The leaves are then discarded, but the liquid is kept and thickened with ash and allowed to crystallize. It turns a deep purple color.
(Source: daeneryus, via askarsloinclothed)