Pandora

Pandora (Πανδώρα in Ancient Greek) was the first woman who was formed out of clay by the gods. She was the one that opened the box (or "Pithos") with all the evils in humanity.

History
Each god helped create her by giving her unique gifts. Zeus ordered Hephaestus to mold her out of earth as part of the punishment of mankind for Prometheus' theft of the secret of fire. All the gods joined in offering her "seductive gifts", Apollo taught her to sing and play the lyre, Aphrodite gave her beauty so Epimetheus wouldn't be able to resist her, Athena taught her weaving and crafts, Demeter taught her how to tend a garden, Poseidon gave her a pearl necklace and promised she would never drown, Hermes gave her deceitfulness, and the box (pithos), and Zeus gave her curiosity.

Before he was chained Prometheus warned his brother not to accept any gifts from Zeus, yet Epimetheus ignored his brothers warning. Pandora is the sister-in-law of Prometheus and the wife of Epimetheus, brother of Prometheus. After Prometheus stole fire from the gods and gave it to the mortals, the gods sealed all the horrors of the world in a box. It was beyond beautiful: inlaid woods of warm and burnished hues, white and amber diamonds encrusted to border the box, green emerald in plaits of golden leaf, purple amethyst with blood rubies and blue sapphires, along with white pearls gleaming in the extravagant sunlight. They gave it to Pandora as a wedding gift, knowing that she couldn't resist opening it because of her curiosity. Because Hermes gave her deceitfulness, she opened the box. In doing so, she released Hunger, Thirst, Poverty, Murder, Death, Jealousy, Sickness and many other evil things into the world. Only Elpis, the spirit of Hope remained in the box.

The Last Olympian
While, Prometheus is talking to Percy he gives him a gift, Pandora's pithos and dismisses the legends of Pandora's "box." He tells him when he gives up hope in the Battle of Manhattan against Kronos, just open the pithos and Elpis will be released, telling Prometheus and Kronos that they had surrendered. Percy then gives it to the goddess Hestia, later when he revisits her in Olympus, stating that hope survives best at the hearth.

Trivia

 * Pandora, a moon of Saturn, is named after her.
 * Prometheus says that she opened a pithos, which is a Greek vase, not a box, contrary to popular opinion.