Door is Chiuso

There is a task you must do here. What lay beyond that open door was the realm of Dark Sentio. It is what they call the Dark Elemental World. I don't know how Usus managed to place his treasure chambers in there, but that's how it is.
The problem here is that the dark force of Dark Sentio has began to seep over to this side through that open door. To close that door again, you must return the <HFFFA7272>Magic Stone of the Battle Square<HFFFFFFFF> to the <HFFFA7272>Torch<HFFFFFFFF> in the <HFFFA7272>Battle Square<HFFFFFFFF>. You are the one who knows that location best, right? Off you go, then. In the meantime, I'll be admiring my treasures.

Why would you hesitate? You should hurry. Altrowise the Corrosion Cave will turn into a hell. Return the <HFFFA7272>Magic Stone of the Battle Square<HFFFFFFFF> to the <HFFFA7272>Torch in the Battle Square<HFFFFFFFF>.

I returned the magic stone. There was not any special reaction. I guess I must return to the surface to find out that everything has returned to normal.