Comoros.
This is a place located between Subspace and the Real Universe. In the crevices of the veil, the Eldar Empire at its peak, with supreme technology, excavated a magical space.
They built a city within it, with the core being the highest crystallization of Eldar technology, the Universe Bones.
Much of the Eldar's technology is based on what is called 'spirit bones.' This is a highly malleable material developed by the Eldar themselves and further processed through technology. It can exhibit virtually any physical property needed by its creator and is used wherever the Eldar require it.
Warships, Battle Armor, Eldar Titans... all these were developed by piecing together spirit bones.
A high-level spirit bone, fused with countless processed materials, gave birth to everything.