It is described as being "so terrifying" that even Giants and Titans steer away from it completely. Annabeth Chase felt that it would be better to look into the face of Medusa than to see the horrors inside. However, it is also the only way for mortals to pass through to the heart of Tartarus while monsters are able to go around using another unknown route that is good for them, but bad for mortals.
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 even more terrifying than looking at 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. 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 which, coincidentally, is the name of the series of books by P.C. and Kristen Cast which heavily features Nyx.
|Underworld:||DOA Recording Studios | Doors of Death | Door of Orpheus | Elysium | Erebos | Fields of Asphodel | Fields of Punishment | Hades' Palace | Isles of the Blest | Judgment Pavilion | Persephone's Garden|
|Rivers:||Cocytus | Phlegethon | Styx | Lethe | Acheron|
|Tartarus:||Mansion of Night | Hermes' Shrine | Chaos|