Zenobia

Zenobia or Throat of Hell is a poison of particular interest because of its painful side-effects to the victim when ingested in food or drink.

It was seldom-used because it was not swift or easily disguisable poison, but it was highly respected because of the excruciating pain. It was recommended for those special occasions when the prospective victim was completely at the assassin's mercy, and the killer wanted to impose a remarkably horrifying demise on his — and often her — enemy.