Dhelmise Special Encounter

==Information==
Location: Wasteland Wall
Available: After Badge 08
==Guide==
You must get the Green Crystal Key from Iolia Valley before proceeding.
If you cannot use Fly outside of battle, go to the 4th entrance to the South from the left (where you fought Fern). Go down to South Aventurine Woods. Go down into Tanzan Mountain.
If you can use Fly outside of battle, go to Tanzan Cove, then go down into Tanzan Mountain and take the left path. 
Regardless, go right into the cave that Saphira created when she broke through the wall. Use the Crystal Key on the Green Crystal. 
Smash the newly-formed Green Crystal wall with Rock Smash and follow the path. Jump down the ledge on the right like in the right photo.
Jump down the ledge in the bottom right corner to land on the wall. Follow the path around, jump off the ledge at the end of the path and exit the cave.
Follow the path on the left side and enter the opening. Push the top boulder and go into the opening in the bottom right corner.
In the new area, push the top boulder right, go down, and push the lower boulder right. Go into the opening in the bottom right corner.
You will end up in a room containing a large amount of boulders. The goal here is to move the boulders in such a way that allows you to activate all 3 machines in one go. If you mess up, simply exit and re-enter the room to reset the puzzle. Upon activating all 3 machines, the tree at the back will disappear and reveal a secret entrance. You only have to do this puzzle once. The right photo shows one way to push the boulders aside to reach all 3 machines.
Go through the entrance and go down the ladder on the left. In the lower floor, go right and down the hole.
The next steps differ slightly depending on whether you have cleared the Wasteland Wall Boulder Puzzle or not.
If you haven't cleared the puzzle, click "Expand" below.
In the new floor, push the boulder right into the hole, and jump into the hole after that as well. 
In the new floor, push the boulder all the way to the right, then climb up the ladder twice.
After that, push the boulder left into the hole and jump into the hole after that. After landing, do NOT push the boulder further left. Instead, go right and jump down the hole.
After landing, jump into the hole on the left. You will return to the beginning. Go right and jump into the hole on the right.
Go right and jump into the hole on the right again. After landing, go right and climb up the ladder.
Push the boulder all the way to the right and jump into the hole as well.
After that, push the boulder all the way to the right, and climb up the ladder three times.
If you already cleared the puzzle, click "Expand" below.
In the new floor, jump into the hole on the right. After landing, push the boulder all the way to the right, then climb up the ladder twice.
After that, jump into the hole on the left. After landing, go right and jump down the hole on the right.
After that, push the boulder all the way to the right, and climb up the ladder three times.
Go all the way to the right and go up behind the tube. Talk to the tube the first time to break open the glass, and talk to it the second time to start a battle with a Level 30 Dhelmise. It does not have any Egg Move in its moveset.
You can also find the Yureyu Key, which allows access to the back rooms in Yureyu Power Plant, and a Toxic Orb.