Locusta (or Lucusta) was notorious in Ancient Rome for her skill in concocting poisons.
According to ancient historians, in AD 54 Locusta was hired by Agrippina the Younger to supply a poisoned dish of mushrooms for the murder of Emperor Claudius. In 55, she was convicted of poisoning another victim, but Nero rescued her from execution and in return called upon her to supply poison to murder Britannicus. Nero rewarded her with a vast estate and even sent pupils to her. When Nero fled Rome, he acquired poison from Locusta for his own use, but ultimately died by other means. After Nero's suicide, Locusta was condemned to die by the emperor Galba during his brief reign, which ended 15 January AD 69.
Locusta's career is described by the ancient historians Tacitus (Annals 12.66 and 13.15), Suetonius ("Life of Nero", 33 and 47), and Cassius Dio (61.34 and 63.3). Juvenal also mentions Locusta in Book 1, line 71 of his Satires.