Overview
The Phantom Moon or Illusory Moon is a red moon visible from inside of a Black Ring. It has hung over the DisSea since the DisSea Explosion and appears to Zoya in her spiritual realm during BR-004. The phantom moon is initially represented by a symbol similar to the Greek letter phi, as on the Illusory Moon Crimebrand, which the Chief says resembles "an eye, a moon, or a fetus" when they see it during battle against the Corpus 002. When the Underground Shepherd consumed Corpus 002, the Phantom Moon seemed to evolve, acquiring a third "spoke" from the center of its circle to the edge. Officially, the existence of the Phantom Moon is yet to be proven. According to preliminary research done by Banyan Medical College, the Phantom Moon is a hallucination that Sinners experience on the brink of a mental breakdown, and does not actually exist in the physical world.
The Phantom Moon seems to possess an alien consciousness of its own and communicates psychically with individuals deep inside BR-000. It possesses a cruel, seductive, and imperious personality, often making promises of power or knowledge in order to lure its victims into traps and then deriding humanity as powerless and insignificant. The moon entity has also appeared to the Chief in the form of the Guide.
The Shattered Battlefront Crimebrand states that "On the day of ruin, the phantom moon shall rise". The Blue Rain crimebrand also refers to a "phantom sun", but nothing else about it is known.
Nightmare Space
The Phantom Moon is connected with a spiritual realm known as the Nightmare Space. A small number of Sinners have reported entry into this space in their sleep, and have experienced memory loss after awakening. Activity in this space leads to immense pressure on the human mind and eventually depletion of sanity. The Nightmare Space is linked to the consciousnesses of the crew of the Keylan expedition. Another prominent feature of Nightmare Space is the Realm Stele, an obelisk located within the expedition's base camp. The Stele's origin and purpose are unknown, but it seems to be of great significance to the Nightmare, providing escape from the Nightmare to the Chief's consciousness when they are adrift there as well as transforming the spiritual realm from its disguised forms mimicking Sinners' memories to its true horrific nature.