Eleanor Carmichael is the Demigod Daughter of Poseidon and a mortal woman. She was born months before the first Great Prophecy was spoken and the oath forbidding the Big Three from having children was made. As such, Zeus ordered that she be brought to Camp Half-Blood for training and monitoring.
When she was thirteen, she was sent on a quest to slay the Nemean Lion. However, she was told by the Oracle of Delphi that she would undertake the quest alone and return later than she anticipated. In Las Vegas, she was trapped in the Lotus Hotel and remained there for fifty-four years before Percy Jackson, Jason Grace, and Annabeth Chase freed her.
Unfortunately, by the end of the Lightning Thieves Series, she is out of her time and trying to adjust to the twenty-first century while on the run from monsters hunting all the liberated from the Lotus Hotel.