The Shanbao Mountain Treasure next to the wall was truthfully a giant mountain, which naturally made it impossible for anyone to move it unless the person who placed the spell on the treasure personally resolved it. The person who placed the spell likely didn't imagine Fang Xing would have a bead so closely tied to the Dragon clan, nor that resolving the spell would be as easy for him as simply turning his own hand.
Beneath the extremely heavy Shanbao Mountain Treasure was a gear that would trigger whenever the mountain was removed, causing a hidden door on the wall to reveal itself and open. Behind the door was a cavern estate of the water clans with a simple layout, with a cauldron, a small pond, and some shelves for manuals. There was nothing else beyond that, making it look like nothing more than a room a cultivator had stayed in for many years while diligently focusing on their studies.