As the Titan Protector of the Young, Leto was the "world's first babysitter", and therefore popular with all the Titans since she would help babysit their children.
Zeus came to fall in love with Leto, and charmed her into having an affair with him, which concluded with her becoming pregnant with twins (Apollo and Artemis). When Hera found out, she cast a curse: no land with roots in the earth could receive Leto when it was time for her to give birth, and yet Leto could only give birth on land. Due to this curse, Leto was driven from land to land, but unable to find a place to rest and give birth. She also caught the attention of Python while trying to consult the Oracle of Delphi for advice, and barely escaped with her life.
Through her children, Leto came to establish a reputation that she was a personage to be treated with all reverence, for no one could behave inappropriately towards her without incurring the wrath of her children: once, when she was traveling to Delphi to visit her son, the giant Tityos attempted to abduct her, but Apollo intervened and slew him with arrows, and even ensured that Tityos' soul was tormented for all eternity as punishment. The second instance was when Niobe, the Queen of Thebes, slighted Leto by claiming that she was better than the Titaness, for she had fourteen children (seven sons and seven daughters) while Leto only had two. To punish Niobe, an indignant Apollo and Artemis slew all of Niobe's children.
Latona is Leto's Roman counterpart. As Latona, she becomes more disciplined, warlike, and militaristic. In Roman mythology, she is the Titaness of Motherhood and Modesty.
Leto was mentioned by her father, Koios, to Iapetus in Tartarus. He claimed that his daughter would likely fight for vengeance alongside the Titans after the way Zeus treated her even after she bore him two twins.
Her son Apollo mentions her frequently throughout the book. He also recalls that she used to call him 'a special snowflake'.
After Apollo drinks from the two springs of memory and forgetfulness to prepare for his trip into the cave of the Dark Oracle, he begins hallucinating, and one of his visions is of Leto kneeling and pleading with Zeus to end Apollo's punishment and allow him to return to Olympus. However, Zeus refuses, saying that his real test is yet to come.
In The Dark Prophecy, Leto was described to have long golden hair that zigzagged down her back in an elaborate ladder weave, and bronze arms that glowed against her white sundress.