The existence of spatial secret realms followed the same principle as fitting Mount Sumeru into a mustard seed.
They were minuscule in themselves, yet could contain mountains and seas.
A spatial secret realm concealed within the layers of space was like a drop of water hidden in the ocean.
Even for a mighty figure of the immortal path in the Heavenly Immortal Realm, discovering a hidden secret realm through primordial spirit perception was exceedingly difficult.
Unless he knew its exact spatial coordinates, he would never find it, even by searching space inch by inch.
That was because every inch of space contained an immense number of spatial particles.
It was just like how every inch of human skin was made up of countless cells.
Under certain special circumstances, however, some hidden secret realms would reveal themselves.
For instance, if an earth-shaking battle took place nearby and shattered space, an attack might strike a hidden secret realm, exposing it.
Or some upheaval in heaven and earth might cause violent spatial fluctuations, forcing the secret realm out of the layers of space.
Some natural secret realms appeared through the second process.
Artificially created secret realms generally had all manner of powerful formations and restrictions laid within them.
If someone actually discovered one and wanted to force their way inside, they would first have to break through those formations and restrictions.
Moreover, most ancient sects and immortal cultivation families stationed powerful cultivators within their secret realms.
The moment they sensed someone attacking the secret realm's formations and restrictions, they would deploy formations to counterattack.
Some secret realms even had "self-destruct" formations and restrictions, which could be triggered if someone broke through by force.
Once a secret realm destroyed itself, all the treasures within would be swept into the spatial turbulence.
The Mystic Yellow