She was born in the ancient province of Gaul. Her early history remains mostly a mystery. 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. Once the drug was made, the task of administering it was given to Claudius's food-taster Halotus. 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.
Her first attempt at poisoning Britannicus proved futile, as the concoction was too weak to kill him. Angry and impatient at Locusta's failure, Nero beat her with his own hands and told her to make a more deadly poison to finish the task. When she succeeded 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. Along with many other of Nero's "favorites" such as Helius, Patrobius, and Narcissus, she was led in chains through the city, and finally executed. Galba had Locusta raped to death by a wild animal (some sources say a giraffe) trained for just this sort of punishment. 
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.
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