There exists a forbidden area in the center of the Zero Dark.
This is where one of the Arks of the Stars, “Velber 02,” punctured the Moon and coalesced with the photonic crystals inside.
In the game, it is sometimes called the “Fragment of the Umbral Star,” but to be precise, it is a starship, deeply buried beneath the Moon’s surface following a crash landing.
It is currently impossible to remove from the Moon Cell, neither physically nor via spiritrons.
Inside it is the stone cavern where Titan Altera sleeps.
The Ark of the Stars itself is an almond-shaped spaceship around six hundred meters in diameter. The cavern that would be its cockpit changes its size according to Altera’s perception of it.
Perhaps to minimize energy consumption, the cavern remains the minimum size required in order to contain Altera.
It appears that the living space allocated to Altera is limited to the area she can “see” under the light that spills in from above.
The inside of the Ark is made of compressed information and is infinitely spacious, so its size adjusts according to by Altera’s state of growth [size].
In the beginning, the cavern was just a space with an overhead source of light. After receiving memory feedback from “Hero Altera” [Attila] living on Earth, it turned into a stone cave with an endless pile of treasure blanketing the ground.