C1989 36 Layers of Space

Because the information in his mind told the cultivators of the Nine States very clearly that at the last moment of the Heart of the World's collapse, it used all of its energy, using the Great Dao of the 36 Heavenly Caves as its foundation, to forge 36 layers of void.

As for the incomparably huge black vortex at the center of the Nine States, it was the entrance to the 36 layers of void