The Vishkanyas

Trained to kill in order to end conflict between kings in Ancient India without causing widespread violence, The Vishkanyas were beautiful but deadly. Oh, did I mention they were women?

According to some ancient documents, they were trained from childhood. They would be dosed with a little bit of poison periodically until they built up an immunity to it. They would then be sent into enemy territory where they would get close to the king and feed them poison, all while eating from the same poisoned dish to eliminate suspicion. The only difference was, these girls were essentially immune. Sneaky sneaky.