[Neus]

I agree with Sarinpa, although the idea of a forced closure after it's cleared has its own problems. For example, if someone else gets to the center first and clears the core, and the person who spawned the dungeon gets kicked out before getting there.

But honestly, the idea of private dungeons with this item is silly. If you were paying for just the one dungeon, maybe, but you can spawn them over and over and over with the key. It's not a one-off thing and doesn't need a bunch of restrictive features surrounding it.