A shadow's width away from the world which, in the future, would hold the countries of Lecolie and Gronorlie, Erryn was bored. She watched a flock of hexauyo wander around a nursery of trees, but the simple fact was that it all needed time. She could form adult animals and plants, but she couldn't form an entire stable ecosystem. What sized population of carnivores could those hexauyos sustain? She didn't know, and the only solution was to wait until things reached their own equilibrium.

While she could start forming sentient life prior to the wildlife reaching stability, she felt it would be better to wait. Alas, it looked like she would be waiting for a long time yet. She needed a project to occupy herself in the meantime, but she'd already poked at the ark as much as she could, and talking to that slime for any protracted length of time would cost an unacceptable price in sanity.

She decided to make a new dungeon. A big one. The biggest. If there were limits, she was determined to find them. No mana-concentrating enchantments this time either; it would be real monsters all the way through. She'd use spatial expansion right from the start too, to avoid hitting the mantle.

The project dragged on for years before she eventually hit floor one thousand. The System didn't have templated monsters for anything above two hundred, but it was a simple matter to create new monster variations adapted for the higher mana. Erryn laughed at the thought of any delvers trying to actually survive these floors; these monsters were outright invulnerable to every skill in the System. Perhaps if it went to rank fifty instead of five, they'd stand a chance.

Monsters aside, there was also the fact that the mana density was high enough to be instantly fatal to anyone, regardless of age or level. In fact, it was so dense that Erryn could barely perceive through it herself. It was like trying to look through dense fog. She had to enclose the dungeon core in multiple layers of mana-attenuating metal simply to stop the thing exploding. Even so, she was looking for the absolute limit, and thanks to these workarounds she was yet to reach it.

The limit turned out to be floor one thousand two hundred and sixty-four. Erryn had made many different materials by infusing mana of various affinities into base metals and substances, but never had she considered that crushing mana itself could create something new. There was an abrupt state-change; the fog collapsed in on itself and the mana condensed, leaving glittering drops of liquid mana floating in the air.

The drops fell, and when they contacted a solid surface, they exploded into bursts of random affinities. All affinities. Whole sections of dungeon melted or froze over, were flooded or collapsed. A burst of body affinity somehow resulted in all the monsters of one room getting glued together into a single impossible, fleshy monstrosity that hurt to even look at. A burst of soul affinity interfered with the local dungeon core and sent Erryn's consciousness reeling.

Erryn caught herself, and managed to shift her perception back to the firework display just in time to see a burst of spatial affinity sending cracks through... something. The mana rushed towards the cracks, which widened hungrily. Erryn honestly had no idea what she was looking at; it was as if they were holes straight out of the universe. She was, briefly, worried; if the cracks continued to widen, wouldn't the entire world be in danger?

Fortunately, the worry didn't last long, because before Erryn could think too deeply upon it, the cracks merged. There was, for a single, impossibly long moment, a hole where the bottom floor of the dungeon should have been. Then it snapped shut, with no sign that it had ever been.

The dungeon core was gone, along with all floors below nine hundred and a significant chunk of the surrounding rock. The earth shuddered as a sizeable cavern opened up in its depths, but nothing had a chance to collapse for more than a few seconds, because at that point the spatial expansion shattered. The remainder of the dungeon suddenly found itself crammed into a space far too small for it, and promptly exploded, sending dust, rocks and boulders flying miles across the landscape. Suffice to say, nothing inside the dungeon survived.

Well, that was certainly an interesting experiment, Erryn thought. It was a good job that she'd done it before populating the surface with any sentient races, or the consequences could have been dire. As it was, no-one was hurt, Erryn had learnt something new, and had had fun doing it. No harm done.

Unfortunately, a certain world not very far away, into which monsters adapted to the mana of four-digit dungeon floors were pouring in through cracks in the sky, would very much like to disagree with Erryn's conclusion that no harm had been done.