A throwable item that produces a short lived Toxin cloud where it lands. It is possible to inflict yourself with this item. How you can carry these and not get infected is a mystery.

The Infested Barbarians in Blighttown drop them fairly regularly. Can be purchase from the Undead Female Merchant for 200 Souls each.

Kingseeker Frampt will take these off you for a return of 200 Souls.