The world was collapsing.
Literally collapsing. When the two top-level powers, which should not have been unleashed, collided with each other, the entire world began to crumble faintly.
In the air, cracks appeared, and beyond them was infinite void.
This bizarre scene made the professionals uneasy and even fearful, but the local fish-monster NPCs seemed oblivious to it all.
Even when some of them fell directly into the cracks and turned into black particles that dissipated, their companions still didn't notice.
This Secret Realm, originally designed for a maximum of fourth-tier abilities, was now bearing pressures it shouldn't have.
The Historical Secret Realm was a memory of the past, as well as an ongoing "ritual".
It had a source of pollution that triggered the ritual and a normal deduction process.
When the content it bore far exceeded its limit, it would naturally disintegrate.