Speculation Twain Manor

When going about Twain Mansion just looking for anything, I decided to go into the fireplace room where you throw the items into Twain's grave. I thought "I wonder if there are hoppers under the other side of the room", where the carpet and enchanting table are.
When I threw items towards the carpet, a hopper sucked it up and a piston opened on the ceiling. There was a ladder conveniently there, so I went up and went in the small hallway. What was this. "Dear family, I hid the skull in a house at a big river"
I haven't seen this before, and since we're looking for clues at Twain Mansion, I wonder if this might be related to ???. If it's an old easter egg, let me know and I'll delete the post.

 

DAMMIT SKRUB, WE WERE THERE FOR HOURS, WHY DIDN'T YOU FIND THIS?

 

https://map.wynncraft.com/#/80/64/-1900/max/0/0
Could be this house?

 

This has been found by me a loooong time ago. This is not connected to ???.

 

Even if it isn't related to ???, we're still horrible hunters for not finding this.

 

Twain Valley isn't. I'm telling you.

 

But did you find what it was relating to?

 

It is an unfinished puzzle relating to the Witherists.