Turath was a type of poison that was used by the Romulans. It left a telltale pungent aroma and was considered a foolproof poison as it worked instantaneously. It was rarely used because of the fact that it left an aroma that warned others of the poison. It could be implanted within the mouth of agents who simply needed to bite down and swallow to suicide. Typically, it was used for merciful deaths or quiet executions. (TOS novel: Vulcan's Heart; TOS - Vulcan's Soul novel: Epiphany)