The strangler

The strangler is a rare and extremely deadly poison, which kills by making a person who has ingested it unable to breathe.

Effects
It causes the throat to swell shut, and to the untrained eye its effects may be confused with a severe choking fit, though it also causes blood to leak out of bodily orifices such as the mouth, eyes and pores. The effects are almost instantaneous after being ingested.

The poison is dealt in the form of amethyst-colored crystals which can be crushed and dissolved into beverages for the targeted victim to drink.