|“||Well, it's the only pig ball I have. So don't ask for encore.||”|
Right before the meeting between the camp counselors begin, she is seen playing got-your-nose with Miranda Gardiner. Lou had actually disconnected her nose, and she was trying to get it back. Eventually Lou gives Miranda it back when Chiron orders her to.
Lou Ellen, along with Will Solace and Cecil Markowitz were sent to spy on the Romans. Lou had wrapped all three of them in the Mist to keep themselves hidden. The three come across Nico di Angelo along the way, and they team up to break in the Romans' camp. Once Nico's distraction was set off, they sneakily entered the camp, and were initially unseen because of Lou's magic.
Cecil managed to sabotage one of the onagers, but the team was caught by a guard when they attempted to recalibrate another one. Will ran off to draw some of the guards away, and Lou turned the other Romans into piglets with her pig balls. Lou, Will, Cecil, and Nico, tried to head for a third onager, but were spotted once more.
Lou warned the others that the Mist wouldn't work on enemies expecting a fight. Nico managed to fend off the guards by summoning an army of skeletons. Lou and Cecil joined the fight, leaving the guards tangled in an odd assortment of ropes and bones. However, the demigods were soon confronted by Octavian, who immediately ordered his guards to fire the onagers.
Lou Ellen was present with the other the demigods in the final battle. She is explicitly mentioned at the end, when Chiron ordered her to turn back the piglets she transformed. Lou obeyed, somewhat reluctant.
Lou Ellen was mentioned to have done Cabin inspection along with Travis and Connor Stoll. During Cabin inspection, she made other people's personal items disappear by manipulating the Mist which later reappeared.
Lou Ellen's appearance is never described in detail, though she may have inherited her mother's dark hair and green eyes along with the rest of her siblings.
In The Blood of Olympus, it is mentioned that she wore a black T-shirt and jeans, with black grease paint on her face like a commando. Binoculars hung from her neck and she has a knife on her side.
Lou is shown to be friendly and welcoming towards others, even Nico di Angelo. She easily gets flustered and blushes a lot. Lou also has an affinity for mischief, as she used her magic to perform various pranks on the other campers.
- She can create illusions.
- She can create false memories.
- She can make monsters invisible or have them be seen as something else.
- She can hide locations.
- She can summon Mistforms.
- She can disguise and hide people.
- She can disguise and hide objects.
- She can influence the minds of mortals.
- She can teleport through the Mist.
- Pig Ball: When defending the camp from the legion, Lou Ellen uses a pig ball to turn legionnaires into piglets. When she changes the piglets back, she does so grudgingly.
- The second part of her name, 'Ellen', means 'Torch'. This could be a reference to her mother Hecate, as her attributes are twin torches.
- The first part of her name, Lou, is a Greek name, however, Ellen is not.
- Due to the translator's mistake, in the Polish version of The Lost Hero, Lou Ellen was introduced as a boy.
- Camp Half-Blood Confidential, Dining Pavilion