1 - Learn the final part of the Song of the Hero from Levias.
Now that you've collected the song fragments from the three dragons, all you really need to do to complete the Song of the Hero is approach Levias in the Thunderhead and dive onto his back. He'll join his memory with theirs to produce the full melody, which you'll use to access one final trial: this one in Skyloft.
2 - Hunt down the Trial Gate in Skyloft.
The Trial Gate in Skyloft is found in the plaza, just at the foot of the Light Tower. Perform the melody together with Fi and you'll open the portal, then thrust your sword into it as usual to warp yourself into the Goddess's Silent Realm.
3 - Clear the trials in the Goddess's Silent Realm.
Collect the first tear right in front of you, then go left up the stairs.
One tear is in front of the Guardian to the left, but watch out for the Watcher.
Go east, collecting another tear in front of the other Guardian, and another one underneath the tree further ahead.
Follow this path all the way around, taking a right once you reach the end of the road, or get in front of the Knight Academy entrance. Climb up via the box and jump over. Watch for the Watcher, and make your way to the left via the small ledge. Climb up the vines at the end and grab the tear in the middle.
Turn right and drop down. Push the block underneath the tear and pick it up. Watch out though - you can only approach it for a few seconds at a time due to the Watcher patrolling.
Go down the stairs now, then drop down to the right. Wait until the Watcher crosses to the other side of the bridge, then go get the tear from the narrow beam.
When the Watcher passes by in the other direction, make a break for it and grab another tear just ahead.
Hop across the platforms and grab the tear near the Guardian there.
Go back across the lake and head left, past the two watchers. Once you go up the stairs, turn left. Collect the tear on the bridge, but be careful that the Watcher doesn't see you.
Follow the path left until you reach a tear surrounded by four Watchers. It's tricky to get, you have to wait or them to spread a bit, so you can essentially dash through and pick it up.
Once you have that tear, go back and continue south up the slope, to the windmill. Drop down to collect another tear. Head out through the doorway (watch out for the expanding and receeding water), and turn south. Go to the graveyard and collect the tear there. You can avoid being initially spotted byt he Watcher by going around, onto the rooftop of the house next to the graveyard, and dropping down on top of the tear from there. When returning, wait for the Watcher to go left, then just sprint up the slope.
Go back to the very beginning, the Tower of Light, and pick up the final tear on top of it. Be mindful of the Watcher patrolling the ladder.
Your Sacred Gift this time: the Stone of Trials! You'll need this to access the hidden resting place of
4 - Bring the Stone of Trials to the lakeside statue to unlock Sky Keep.
According to Fi, this stone is part of a set. You'll need to find its twin to unlock the Sky Keep where the Triforce was placed by the Goddess. There's only one other stone that fits this description: the one set in the eye socket of a statue nearby the lake. To place the Stone of Trials in its other socket you'll have to face the Goddess Statue - and for good reason. When the stone clicks into place, the temple beneath the Goddess Statue descends, revealing the entrance to Sky Keep!
Cross over to the doorway using the Clawshot targets that appear and prepare to search the twisting, ever-changing mazes for the Triforce...
5 - Recover the Triforce of Courage.
The Sky Keep is incredibly confusing for first-timers. If you want help solving the dungeon's puzzle, make sure you DO NOT manipulate the dungeon without following these specific instructions. Making any moves otherwise will make it very difficult to replicate this solution to the dungeon's massive puzzle. You have been warned.
The Dungeon Map is sitting in a chest in the middle of this first room. Why? Because you'll need it to guide you to the things you need to complete the dungeon. Notice that not all of the doors to each room line up. That's because you can shift the rooms around using various tablets scattered throughout the temple. One of these is through the passage to the right.
You can only move one room right now since the one you're in is fixed, so slide it down into place and move the one that was to he left of it into position to create a second passage. Then proceed through the door to the east to start making your way into the temple.
This room is based on a combination of the forest area and the Ancient Cistern. Hang a right and fight your way past a few enemies to reach a wide gap. A hanging bar you can use your Whip to latch onto will help you cross, but you'll need to sever the grass the rope up ahead is tied to so you can leap between your Whip and the rope to make it all the way to the other side.
Your Clawshot can help you climb higher thanks to the vines nearby, so go as high as you can until your progress is halted by the Pyrups breathing fire from their safe alcoves in the wall. You can blow them up by grabbing Bomb Flowers from one of the rotating pillars with your Hook Beetle. Take a leap onto the hanging rope and swing over to the suspended platforms. Your Gust Bellows can set them swinging so you can reach the ledge on the far side of the room. Pull the lever here to create a shortcut back so you don't have to repeat that ordeal.
Head left and pick up the Timeshift Orb, then turn around and go down the stairs. Drop the orb so you can climb the ladder and pull the lever at the top, then, drop down, recover the orb, and stand on the pressure switch to open a hatch that lets you drop the orb on the nearby conveyor belt. Toss it there, then ascend the ladder a second time to follow it to the other end of the belt. Another pressure switch here will open up the other hatch so that the orb rolls out.
You might recognize the pronged platform up ahead from the Lanayru Mining Facility. Drop the orb onto the platform, but disembark and head along the left-hand wall so you can move the platform along with your Gust Bellows. Step on the pressure switch about halfway down the room to open up the gate blocking the platform. When the orb nears the end of the track, it'll reveal an arrow switch that you can hit to open the gate to the next room. Recover the orb and proceed through.
Pull the lever to create a shortcut to the place where you first entered this room. Then approach the nearby conveyor belt and step on the switch to open the bottom hatch so you can toss the orb on. As the orb travels along the belt, it'll reveal a set of five arrow switches along the wall up above. Shoot them as it passes each to unlock another tablet that can manipulate the rooms in this dungeon. If you need to, you can pull the Whip switch to reverse the direction of the conveyor.
Use the tablet to shift all of the rooms in the two left columns clockwise one space, then move the now-middle space down one additional space. Next, slide the room now at the middle-left space to the center and the room in the bottom-left corner to the middle-left space. Backtrack through the forest room to enter a new chamber.
Head left and crawl into the small opening. Take a left at the crossing and, once outside, roll a bomb back into the tunnel to blow the other way free. Crawl through there and burrow down the mound. Go forward and hit the piston, the head back. Dig out of the hole and crawl back through the opening, the turn left. Kill the Lizalfos and throw a bomb into the statue's pot to make it fall over. Do not activate the crystal yet though. Roll a bomb down the slide into another statue, then slide down yourself, you'll land on it. Hit this switch here and climb up the vines. Using the skyward slice, cut the trees on the two small pillars to your left. Using the Beetle carry a bomb from the right pillar to the pot of the statue on the left pillar. Do not activate this crystal either. Instead, activate the crystal you discovered first. The way back to that area is straight ahead, just jump down from the south edge. After you activate that, use the Beetle to go back up and activate the last crystal you discovered behind the trees.
Enter the door that opened next to the first crystal you discovered and burrow down the mound. You'll use the bomb in the middle to destroy both the rock on the right and on the top left. To do the forer, just push it twice from the left side. The latter however requires you to push the bomb from the left, then quickly sprint crawl around the bottom and push it again. Go around the top and push the blue piston in, then go back the way you came and leave the underground. When you exit the room with the mound go right, and now take the newly opened left path on the crossing. Follow it and enter the mound.
You'll battle an enemy that's nearly identical to Scervo in the narrow room ahead. It's called Dreadfuse, and it was put here to guard the key leading to the Triforce of Courage. Fight it off with the same strategy you used on the Sand Ship and pick up the key from the chest. Then head through the door on your left to exit to another portion of the chamber.
At the tablet here, move the rooms oriented around this room counter-clockwise two spaces each so that the Courage room lines up with the west door of this room, then proceed inside.
Triforce of Courage Room
Go to the middle of the chamber and enter the locked door. You'll face a gauntlet of enemies from all over your quest: Moblins, Bokoblin Archers, Stalfos, Bokoblin Chiefs, and finally a room full of Cursed Bokoblins and a Stalmaster. Typically it's best to deal with the weaker enemies first to get them out of your hair so you can focus all of your energies on the primary enemies. This is especially true for the Stalmaster, who's terribly difficult to fight with Cursed Bokoblins in your way.
Defeat all the enemies and thrust your sword into the Farore crest at the center of the room to access the Silent Realm containing the Triforce of Courage.
6 - Recover the Triforce of Power.
Backtrack to the room where you found the key and approach the tablet again. Rotate every room counter-clockwise again so that the Power chamber lines up with the west exit of this room.
Triforce of Power Room
Head left and pop the water fruit to create a platform. Ride it and hit the switch on the far right once it comes into your view. Once you get close to the crossing, hit the water fruit on the other side to create a platform. Jump on the newly created platform and hit the switch above the stone head to stop the magma flow. Ride the platform and jump off on the left ledge when you reach it. Pull the lever to open up a shortcut to the begining of the room. You'll be doing something similar as before now - pop the water fruit and ride the platform. Near the of the corridor look to the right and hit the crystal switch above the demon head with an arrow. Then hit the water fruit and quickly jump across to it. Ride it around the curve and jump onto the rising platform when you get close enough.
Send back the Beetle and hit the crystal switch again, to toggle the other lava stream, the one you now need. Hit the water fruit straight ahead and jump onto the platform. Ride this last platform until the end of the corridor and grapple yourself to the left side once the grappling points gets into view. Thrust your sword into the symbol of Din and take the Triforce of Power in the Spirit Realm. Once you're back outside, pull the lever to create a shortcut and backtrack to the key room.
7 - Recover the Triforce of Wisdom.
You'll want to undo all the movements you've made from this room, so flip everything back clockwise three spaces (the Wisdom space should be at the top-left corner), then head through the west door and you'll emerge in the room where this all started. Shift the bottom-center room to the left, then rotate all of the rooms on the outside perimeter that can be moved one space clockwise, so that the Wisdom room is now at the top-middle of the dungeon. Next, backtrack to the key room and move the two rooms on the left column up one space so that you form a connecting path from this room all the way to the Wisdom room.
Triforce of Wisdom Room
Sprint right and up to the timeshift orb. Take it to the opposite side of the room and place it on the small mark on the ground. Go back to where the timeshift orb originally was and from there shoot an arrow into the switch on the opposite wall (Previously inaccessible). Get the orb and head through the newly opened door. Make your way slowly through the corridor, but leave the timeshift orb a few meters back, just so you have enough room to spring across the quick sand to solid ground. Stand on the switch at the end of the way and shoot an arrow at the target through the propeller opening.
Head back and, with the orb in hand, go to the far right, where it was originally placed. If you approach the faraway edge, a couple of pillars will appear on the left. Jump onto them so that you're aligned with the grappling point on the east wall. Before you grapple there though, throw the timeshift orb forward, so that it covers the room with the grappling point as much as possible. If done right, the door to the Nayru symbol should be open.
8 - Use the Triforce to destroy Demise.
You've done it! You've completed the Triforce! Your wish on its power will send the Sky Keep tumbling down into the Sealed Grounds, utterly crushing Demise for good.