Erauso is the author of the autobiography Lieutenant Nun. The book covers 25 years (1600-1625) in which she escaped from her convent, donned men’s clothes, adventured around South America, confessed her identity to the bishop of Guamanga, and was eventually granted permission to remain in men’s clothing by the Pope. This record is the main source for her life, and much less is known for certain outside of the period it covers. What is known is that in 1630, she returned to South America to live the rest of her life, going by the name of Antonio de Erauso and working as a mule driver and small merchant. There is no exact information on when she died, but it is believed to have been sometime in the 1650s.

Erauso is the narrator and the figure through whom the main themes of the book are expressed. However, Erauso introspects very little throughout the text and gives almost no hints as to her motivation in any given moment. When Erauso does mention a reason for an action, it is either necessity, as seen with her fleeing towns she had committed crimes in; offence and anger causing her to battle over an insult; or a desire to seek adventure, as shown when she joined the army because “[she] had a mind to travel and see a bit of the world” (17).