|Stories||Kingdom Hearts: Shadows of Eternity|
|Theme Music||End of the World|
|Battle Music||Fragments of Sorrow|
"You had a world inside your heart-- now see for yourself the world inside mine." - Cleopatra Endellion DeBuio
Unborn Core makes its only appearance at the end of all three characters' storylines. Nearly every location in this world is dark and bleak; plants are gray and lifeless, mountains are black and unforgiving, and water is still and unnatural. It may be argued that each room represents a particular emotion Cleo felt during her journey to join with Anthony and create the χ-Blade, since this world is truly an Unversed world. The sole exception to the trend is The Thirteenth Sanctuary, which may not even have been created by Cleo.
When Anthony is first dragged here, Cleo deposits him at the Ocean of Sorrow and informs him that this world is his "final test". Driven by the resolve to end Cleo's terror campaign, Anthony makes his way through the world to confront her. When they do meet, Cleo reveals a trap and has Unversed hold him down while they join. Forced deep within himself into his Dive to the Heart, the two battle furiously as Cleo wields an incomplete χ-Blade, but is defeated in the end as Anthony draws on the memories of his friends and adventures.
Though Cleo is defeated by Anthony, Lily arrives later on at the Unborn Core searching for Anthony. As she makes her way through the world, she is accosted by the voice of Cleo telling her that she is doomed to fail and that the χ-Blade will soon belong to her. Inspired by fear for the safety of her friend, she makes it to the Heart of Darkness to see Cleo's Remnant preparing to fuse with the unconscious Anthony in an attempt to make the χ-Blade. Interrupted, it attacks her, but Lily triumphs and vanquishes the Remnant. Taking Anthony and escaping, the world shudders and begins to seemingly collapse.
However, it does not disappear; Alex comes last, after visiting their home world of Spellbound Ascension, and makes her way through the rooms. At the end of her journey, though, she enters The Thirteenth Sanctuary to find herself face-to-hood with the Unknown. It speaks without actually talking, and tells her that, though she and every other Key Bearer before her has tried, nothing they've done has derailed its plans in the slightest. Angered, Alex attacks, but every Keyblade she tries to use is simply shrugged off by the Unknown. Finally, Alex uses her Kingdom Key, and the final battle ensues. Though she defeats the Unknown, it simply fades into the shadows, saying that "not even this defeat will change the future".
- Ocean of Sorrow - A beach on the edge of a vast dark ocean. The water is solid somehow, allowing you to walk on it. Only Floods appear in this area
- Forest of Doubt - A dark and foggy forest filled with gray trees and the sounds of wistfull sighs. Only Archravens and Hellbats appear in this area
- Glade of Guilt - A wide open plain filled with nothing but gray grass under a purple sky. Only Bruisers are found in this area
- Canyon of Discord - A deep craggy canyon with a dried up riverbed at the bottom. Only Scrappers and Toadstools appear in this area
- Caverns of Betrayal - A dark cavern with purple luminescent crystals growing from the walls. Only Hareraisers and Chrono Twisters appear here
- Lake of Peace - A placid subterranean lake in a cave with pink walls, as well as blue luminescent crystals growing from the walls. The water appears to be green. This is the location of the only save point, and on rare occasions, Shitakis will appear
- Mountains of Madness - Tall mountains made of black stone with a purplish-black overcast sky overhead. The path carved into it is uneven and erratic. Only Mandrakes and Axe Flappers appear in this area
- Heart of Darkness - An area that seems to be nothing but swirling waves of darkness. Somehow, there is a solid ground for you to walk on in this place. Cleo's Remnant is fought here
- The Thirteenth Sanctuary - A stark contrast to every other location in this world; it is a marble room lined with columns which stand in front of solid white walls. At one end is a large throne with two Keyblades embedded in it, and on the walls are alternating symbols of the Unversed and the Keyblade Masters. The Unknown is fought here
Note: Enemies in Bold are bosses.
- Chrono Twister
- Axe Flapper
- Cleo (Boss)
- Cleo's Remnant