The Annihilation Tower Secret Realm had originally been a demon-hunting space fragment assigned by the Seven-Ring Holy Tower when Green became a Demon-Hunting Wizard. At the time, it had merely been used to store personal belongings, but Green later turned it into a World Laboratory.
A dead-silent sea, a single island.
Not until Green brought in the Golden Tear Ginseng tree and the Dewflower Spirit did the fragment space finally gain some vitality.
Later, the secret realm grew larger and larger, its area expanding time and again. Green even developed the Nineteenth-Layer Abyss Laboratory, cultivated all manner of experimental creatures, merged in more intact ancient secret realms, and even held exploration reward events for academy wizard apprentices, much like Green's own expedition into the Black Isotta Secret Realm after the Regional Academy War.
These secret realms and space fragments had originated during the first War of Civilization. To defend the Wizard World against the Nightmare Alien Civilization, True Spirit Wizards used themselves as bait to defeat the nightmare aliens. In the end, even the world itself had completely shattered. Since then, these fragments had surrounded the Wizard World like guardians.
During the second War of Civilization, Antonio pried the Wizard World loose. These fragments followed the Wizard World to this unfamiliar world cluster, embarking upon a new journey.
"Why not use this time to set up a Dimensional Gap Sealing Art here? Ga ga ga ga! With your abilities, if you could seal an Orbital Planet-Destroying Ship, perhaps you could..."
Little Eight egged Green on.
Come to think of it, it was not only Green. Most newly advanced Stigmata Wizards probably had not made any extensive arrangements in their secret realms. Newly advanced Stigmata Wizards simply had not considered that these secret realms were themselves part of the Wizard World's