Talk to the Innkeeper to ask about the cursed chest:
Ask about the cursed chest
Wait, what do you know about a cursed chest? And how did you know I have it? Did those snooty Sea Scholars tell you? My word! They just hand out information like it's candy these days it seems.
Well, they told you correct. I do have the chest and I've been trying to open it for years. Unfortunately I can't. I thought that all you needed was a key but it turns out there's a bit more to it than that.
You see, the curse put upon on this chest isn't any old curse. It has...well...connections. The chest can't be opened without certain items. In this case, rings.
When I found out it couldn't be opened merely by the moonrock key, I began doing extensive research into the matter, trying to find any clues on how to open it. Eventually I came across some information regarding two rings. Apparently whoever put this curse on the chest tied the curse with two rings, one known as the Ring of Night and the other known as the Ring of Day. These rings are rumored to come from the ancient days and as such can probably only be found in ancient chests.
Unfortunately I now have my time tied up in running this inn and my adventuring days are quite behind me. I guess you can have the chest now. It doesn't do any good seeing it sit here, gathering dust.
Remember, to open the box you'll need a moonrock key, and either a Ring of Day or a Ring of Night. According to my research, the contents of the chest can change depending on which ring is worn during it's opening. Good luck to you.
Once you have the moonrock key and one of the rings equipped, open the cursed chest to receive the jewel corresponding to your ring. Be aware that you cannot receive both jewels in a single save, since you can only have one Calamite Ore and one Cursed Chest !