The relic that you found on Dragonhead Island leads you to the Depths, where you find the Construct Factory.
Put the Owl Mask in Place
Use Ultrahand to move the Mask into the slot where the beam of light is shining.
Mark the Storehouses
From the place where you put the owl mask, you can see all four storehouses, so you might want to use the Scope to put a pin in each one before you proceed.
The storehouses can be done in any order. This section is for the southeast storehouse. There are some Bokoblins between you and it, so either go around the Bokoblins or defeat them to reach the Left-Leg Depot.
Check on the glowing object and a left leg will fall from below. Attach it to an angled platform and hit a rocket to launch the platform upward. Move the left leg to the upper area.
You can optionally use the Device Dispenser nearby.
Push the wheel to lower the ramp until it is aimed at the opening above the water. Place the left leg on this ramp, then attach a rocket to the bottom of the left leg container, and hit the rocket. Then go into the niche in the far wall and use Ascend to go up to where the left leg ended up.
Retrieve the left leg from the end of the water area. You will see some beams that are blocking the top of some stairs nearby. Stand on the platform with the rockets, and hit a rocket to be launched upward. Use Ultrahand to move the treasure chest through the beams and bring it to you. Then move each cart through the beams, one by one. Place a cart in the straight path down below that points back at the Construct Factory, so that the cart's wheels are pointing toward the factory. Attach the left leg container to the top of it. Then attach the second cart behind the first to make sure you don't fall off of the back of the cart when it is launched forward. Then attach a rocket to the back of the cart. Hit the cart to start the rocket, and you should be launched to the factory with the left leg.
Detach the left leg container from the cart, put the container on the ground near the incomplete owl mask construct, and the container will open automatically. Place the left leg in the glowing opening beneath the owl mask, making sure to rotate it so that it fits correctly.
The storehouses can be done in any order. This section is for the southwest storehouse. On your way to the southwest storehouse, beware of the three Evermeans that are pretending to be trees along the route. Use fire or sharp weapons to deal the most damage. Then go up the slope and enter the storehouse.
Check on the glowing object in this room to receive the left arm container. Hit the wheel on the chain to open the door, then use Ultrahand to move the left arm through the door.
Detach the two wheels on this side of the door and place them somewhere so they won't roll into the lava. Then place the left arm container flat on the metal walkway near the lava. Attach the two wheels to each side of the left arm container so that the arrows are pointing to the lava. Attach the control stick to the top of the left arm container. Then jump onto it and drive it across the raised layer of lava.
Move the left arm container to the next area. Before you continue, use Ascend to reach the platform in the corner, where you will find a treasure chest. Then go back down, and rotate the left arm container so that its front is the wide side. Detach the two wheels and put them on the two short sides of the container. Detach and rotate the control stick, then attach it to face forward. Then drive the cart so that the wheels are on the lava while you are in the middle of the two pieces of metal along the path.
At the end, go up the ladder to find a Grand Poe. Then go back down and detach the two wheels from the left arm container. There are two chains hanging down in front of the door. Let them hang where they are, and attach a wheel to the door, with the arrow pointing toward one of the blocks at the end of the chain. Once the wheel is attached to the door, take the stone block at the end of the chain in front of that wheel, and attach that stone block to the wheel. Hit the wheel, and if you did it correctly, the door will go up. Just remember that you need to attach the wheel to the door, and the stone block to the wheel.
Move the left arm container through the open door. There are two wheels here that are being spun around by fans. You will notice something attached to one of the wheels. Hit the fan that is spinning that wheel so that it stops spinning. Then you can detach the chest from that wheel and open it.
Now make sure there are no wheels attached to the left arm container, and detach the steering stick, and rotate it so that the narrow part of the container is the front. Attach a fan to the back of the container. Then put it in the nearby water and use the controls. Follow the waterway to the end. Let go of the controls to defeat any Constructs that attack, then take the container out of the water and move it near where you put the owl mask. The container should open automatically. Then use Ultrahand to put the left arm in place, making sure to rotate it to fit correctly.
The storehouses can be done in any order. This section is for the northeast storehouse. If you go east from where you put the owl mask, you will find a construct guarding a bridge made out of bone. Go up this bridge to reach the Uisihcoj Lightroot, which you can reach using Ascend. It will light up the area with the northern storehouses.
From Uisihcoj Lightroot, go east, defeat the Aerocudas and Bokoblins, and go east to the stone platform. Go south along the platform, then glide south to the next platform. Then glide east to the entrance of the storeroom. This is the Right-Leg Depot.
Examine the glowing object up ahead to receive the right-leg container. Place the container onto one of the platforms that has fans attached to it, then stand on the platform and hit the fans to go up. Move the right leg container off of the platform.
There is a rail here, and a U-shaped hook hanging from the rail. Attach the right leg container to the side of the hook, not the bottom, so that the opening of the hook is on the left, allowing it to go past the metal pieces that hold the rail in place, without getting stuck on them. Then attach a fan to the back of the right leg container and activate it. Then go to the south end of the room and use Ascend to go up to where the right leg container went.
Hit the fan to turn off the power, then climb up to the upper area where you can see some Wings. Open the treasure chest here to find some Zonaite, then move a Wing down to the lower area, and a steering stick if you need one. Go down to the right leg container, then detach the fans from the nearby platform. Attach the right leg container to the top of the wing so that the wide side of the container is the front, then attach fans to the back of the wing. Attach a steering stick to the top of the right leg container. Then place the Wing on the flat rail that points west (if you place it on the rail that slopes downward, the wing might get too far away before you can hop on) and use the steering stick to fly the Wing to the Construct Factory. The wing may continue to fly forward after you let go of the controls, so be sure to fly toward a barrier so it can't go too far away.
Detach the right leg container and move it in front of where you put the owl mask. It will automatically open. Use Ultrahand to move the right leg into the glowing spot, making sure to rotate it to fit correctly.
The storehouses can be done in any order. However, the path to the northwest storehouse will be in darkness until you activate Uisihcoj Lightroot. See the Northeast Storehouse section for directions to the Uisihcoj Lightroot.
From where you put the owl mask, go west along the stone wall in the water. Go to the area beneath the storehouse door, where you can use Ascend to reach the storehouse door.
Examine the glowing object to receive the right arm container. Place the container on the ramp going up, and the wheels will take it up the ramp. You can stand on the container to go up, or just walk along behind it.
You can go to the area below the electrified column, and go through the tunnel beneath the far end of the electrified column, to find a chest that contains a Large Zonaite.
Go back to the right arm container. Place it in the groove on top of the electrified container, then take a wheel and attach it to the right arm container so that the wheel will move the right arm container along the top of the electrified column. Then go down to the lower area and climb the ladder on the far side, where you can remove the wheel from the right arm container.
Move the right arm container to the next area. Take one stone slab, place four wheels on top, all pointing in the same direction, and flip it over onto the wheels. (Don't attach two slabs side by side, because the resulting cart would have a hard time going up slopes, which you will need to do.) Attach the right arm container to the top of the cart, then attach a steering stick to the top. You will need to ride the cart down the gloom-covered slope, but beware that there are bokoblins and a boss bokoblin up ahead. If your cart gets stuck, you might not be able to get away from the bokoblins and will have to try to move to a clearing in the gloom to fight them.
When you reach the Construct Factory with the right arm container, take it to where you put the owl mask, and it will automatically open. Use Ultrahand to place it in the glowing opening, making sure to rotate it so that it fits correctly.
After you Complete the Construct
After the Construct is complete, you will use its abilities to reach the secret stone.