Delivering the Black Key

Looks like you've received something from シャモス. Thanks for your work. Now all you have to do is deliver that package to me. Oh, you don't need to come all the way to see me in person, though.

There's a 隠密な岩 on the far right side of エルナス. Just put the item under it, and another member will come and retrieve it.

Hmm. Alright, I'll assume you are very busy at this time. But don't make me wait for too long.

(There is a tree stump that looks rather suspicious. When you reach into it, you notice that it is hollow, as if man-made.)

(You push the key into the hollow space inside the tree stump.)

(The stump looks just like any other tree stump.)

(There is a tree stump that looks rather suspicious. When you reach into it, you notice that it is hollow. It is man-made. 暗黒の影 told you to put the item there.)

You've yet to find the 隠密な岩? All you have to do is place the item you received from シャモス on the far right side of エルナス.