Percy Jackson and Annabeth Chase narrowly escape from Akhlys by jumping off of a cliff into Nyx's territory. They distract Nyx and all of her terrifying children by tricking them into creating pitch-black darkness around them, after which Percy and Annabeth run towards the Mansion of Night.
Even most of the Titans and Giants are too terrified to go near the mansion, as Polybotes refuses to follow Percy there, and Iapetus describes it as being "too scary." Thus, Percy and Annabeth run through the mansion with their eyes shut as Annabeth feels that it would be more terrifying to look at than the face of Medusa. After running through, the two demigods come to the River Acheron, and Percy barely manages to jump over it, with Annabeth along with him. After leaving the realm of Night behind, they both resume their journey to the Doors of Death.
- In chapter Twenty of The Blood of Olympus, it is mistakenly called the House of Night.