Task 1: The Four Poes
You cannot stand in the dungeon's sandy floor for very long without being consumed by it. Fire your clawshot at the east wall's round grate to get to a safe platform. Then jump across platforms and run over short stretches of sand to get to the chamber's northwest corner. While standing on solid ground, grapple the chain with your clawshot, pick it up, and pull it back to make the gate open.
In the next room, fill up your lantern (and an empty bottle if you feel like it) in the pot of lantern oil to the west of the locked door. Head to the other side of the room and break open the wooden barrier, then collect the key. Small insects proceed to swarm you, so swat them away with spin attacks or use your lantern as you head to the door. (The insects hate light and will not come near you if you have it out.) Open it and head through.
This dark room has two unlit torches on the far side. Avoid the holes of sinking sand and defeat the hordes of stalkin as you light the torches. After the torches are lit, you are able to go into the next room.
In the central chamber, four poes appear before you, then three of them leave. Transform into a wolf and take on the remaining poe. Jump onto it with and continually press to maul it. Eventually, the poe will become free of your grasp and turn transparent. Wait for it to become solid again before attacking it. The second round should finish it off, allowing you to take its soul with (it revives itself if you don't).
Inspect the remains of the defeated ghost to learn the poe scent, and follow it to a patch of dirt. Digging there reveals a chain that you can pull to make a set of stairs to the basement to appear. Before you head down, open the room's two treasure chests. The one in the east holds the dungeon map, and the one in the west contains a piece of heart. Use the clawshot to return to solid ground after collecting the treasures, then head down to the basement.
Another one Bites the Dust
A flat appendage sticks out of the pillar in the round room downstairs. Push it to make the pillar turn and a door open, revealing an alcove containing a key and a ReDead Knight. Attack the knight from afar with bomb arrows or a jump attack in wolf form, then take the key. If you get too close to the ReDead Knight, it freezes you.
Stand at the north end of the round room, engage your clawshot, and look up. Aim at the round grate through the hole in the ceiling, and grapple up to it. Head north into the next room and defeat the poe there the same way you defeated the last one.
The Third Poe
Head back the way you came (turning the pillar to give you access to the stairs), and engage your senses in the main room to reveal two paths. Follow the path west past the pillar and through the locked door (you can open it using your key while remaining in wolf form).
In the next room, go across the north end to get to the west side, moving across the sand from one platform to the next. Spikes occasionally pop up from the sand, so either move slowly or use your wolf senses to see where they are. Once across, pull the cage east then north to fit it between the raised platforms. Walk up the stairs and hop over the wall to the west. Pull the chain back to make the chandelier rise. Let go of the chain when it is all the way back, then run under the chandelier before it falls.
Head up the stairs and past the pillar to collect the compass, then return to the pillar and push the part that sticks out from it to reveal openings to the east and west. Head west, cut through a wood barrier, and defeat another ReDead Knight to get to a small key. Use the key on the locked door to the east, transform into a wolf, and take on the groups of Stalkin and two ReDead Knights (some prefer to do this as a human, because of the ability to use bombs). Then follow the scent to a chain under a patch of dirt, and pull it to reveal the dungeons third poe. Defeat it like the others, then head north.
The Final Poe
In the circular room, grab the key from the chest in the south side, then engage your wolf senses. Use Midna's dark energy or a spin attack to defeat the phantom rats, then travel east through the locked door. Engage your senses to see a scent trail that floats over the room. Follow it, going over a chandelier, and into the next room.
Walk down the stairs, push the cage until it sets in place, and pull a chain to make the chandelier rise. Walk under the chandelier and let it drop around you (stand on the indented portion of the path). Climb from the center to the east, then continue through the door. The next room contains a Stalfos. Defeat it like you would any other enemy, then plant a bomb by its bone pile to destroy it for good. If you take too long with the bomb, the Stalfos will regenerate itself. Bomb arrows work too. Head south after it is dead.
The next room contains a bunch of torches, two of which must be lit to proceed onward. Light the one that is not in the row, and the one farthest east. If you light any torches other than those, you will be attacked by a multitude of skeletons. After lighting the correct two, head west past the section of wall that was previously there.
You finally found the final poe, but defeating it won't be as easy as the other three. The poe splits into four ghosts that revolve around you. The real one shines just a tad brighter than the fakes, so attack that one. After two rounds, the poe goes down and allows you to take its soul. When you return to the main room (head north into the next room, then west, the gate at the north end will open. Travel north from there.
Task 2: To the Boss
The Torture Chamber
Find the shaft in the northwest section of the first floor. Drop to the platform near the bottom and push the center pillar's appendage counterclockwise for two full rotations to make the platform rise to a path that holds a small key. Then push the lever clockwise to have the platform sink to the bottom of the shaft. Open the locked door.
The next chamber houses phantom rats, hidden spikes, and sinking sand. Use your senses to see the rats and glowing outlines of the spikes. Defeat the rats and head to the southwest side of the chamber. Clear the area of the phantom rats and a ReDead Knight, then pull the chain to slide the wall out of the way. Run around the spikes and through the opening.
Head east through the chamber, avoiding the rolling spikes along the wall. Slice through the swarms of bugs, then defeat the Stalfos. Ooccoo awaits you in a pot nearby. Move north through the middle section of floor B2 in human form and into the round chamber. A closed gate on the west side features a spinning spiked pole. Run around it through the opening to the north to take on three Stalfos. Attack the two that are out in the open, then cross the sand to get to the third. Once the gate is open, return to the round room with the sinning spiked pole and head west. Follow the path until you reach the door to the north, then head in.
Miniboss: Death Sword
When you enter this room, you'll find a large sword sealed up with sealing charms. Allow yourself to accidentally cut one...
As soon as one rope is cut, the sword comes to life. It burns away all its other seals, floats into the air as if nothing is supporting it, and takes a few aimed swings at you. Transform into a wolf and engage your senses to see the swordsman wielding it. Just like the poes, he will glow, so attack him in wolf form until he becomes visible.
With his cloak gone, the miniboss, Death Sword is revealed, angry and relentless. Now exposed, he flies around the room. Return to human form, dodge his gaseous projectiles, and then shoot bomb arrows at him. He drops to the ground after a single hit, he will raise his sword and try attack you, so dodge his attack and his sword will be stuck in the ground. Strike him with your sword and he will try to attack from behind. Dodge his attack again and while it is stuck he will not be able to retaliate.
After he takes the clobbering of his afterlife, the monster lets out a blood curdling roar and dissipates into a group of Keese, flying away in retreat, while the sword breaks into pieces. With Death Sword gone, you'll find a secret path to a chest. Open it to get the Spinner.
With the fancy-looking Spinner, you can ride it around along tracks on walls to reach new heights and cross pits, attack enemies, and use it as a key to unlock secret passages. To get out of this room, ride the spinner up the track to the exit.
Tracks of a Heart and a Key
In the basement's northeast corner, float over the sand with the spinner to reach the first of two treasure chests shown on your map, then ride a track on the right wall to reach a chest that holds a piece of heart. Fight or avoid the nearby Stalfos, then take the track on the north wall to get past the spinning spiked stick. Hop from track to track with the button to get to the northern half of the room. Stop spinning for a moment when you find yourself going in circles, then head back the other way along the track.
Four small spinning spiked mechanisms ride the tracks between the chamber's northeast and northwest corners. Hop from track to track to avoid them. When you reach the other side, you'll have access to the room that houses the big key.
Gear it Up
Head west to go to another round room, then use your spinner in the gear-shaped hole. Press repeatedly to activate the mechanism under the floor that turns the wall, giving you access to the northern shaft.
Go to the room in the north and ride the track up as far as it goes to reach a fairy, then go back down to the place that overlooks the part of the center pedestal that juts out. Jump to it with a roll-jump (roll off the ledge), you'll likely catch it with one hand. Another way to get to the center pedestal is to use the spinner from the same over look. Climb up and use the spinner on the center indentation. The pedestal will rise up to another track. Ride that one up as far as it goes, and you'll reach the location of the boss.
Twilit Fossil: Stallord
When you enter the boss room, a large, lifeless skeleton sits in the darkness. Run to the giant skull in the center of the room to prompt Zant to animate it. Now, with life coursing through it again, the vanquished STALLORD reawakens.
Part 1 Strategy
Stallord may seem deadly, but time has reduced him to half a skelton and a crumbling spine. In the first part of the battle, Stallord is stuck in the middle of the room. Hit its spine with the spinner to slowly shatter it. Ride along the track on the area's perimeter (hopping off when a spikey thing approaches), and drop to the skeleton when the way is clear. Press to attack its spine. After you hit Stallord a few times, the number of his Staltroop minions surrounding him will increase. Eventually Stallord will fall, lifeless again. As the sand pit drains, only his head is left.
Part 2 Strategy
Use your spinner to raise the pillar in the center of the arena. This will change the entire layout of the room. However, Stallord still has a little fight left in him. The skull will come back to life again and knock you off. Start spinning up the inside tracks to pursue the skull, then jump between tracks to avoid Stallord's fireballs. When you are close to the skull, jump to hit it with the spinner. The creature drops to the floor, so follow suit and hit it with your sword. After every round, spikes will be added to the tracks, jump between tracks to avoid them. After a few rounds, it flies to the top of the room, before falling back down and bursting into twilight, netting you a heart container.
Aftermath: The Mirror of Twilight
A Shadowy Battle
Head to the top of the central pillar. Midna tells you that you are close to the Mirror of Twilight. Head outside and climb to the top of the building to discover a huge statue. When you get to its base, five shadow beings create a force field around the structure then attack you. Transform into a wolf and dispose of them with Midna's dark energy, or destroy them in human form with spin attacks.
To the Top
Following your victory, head to the top of the statue via the spinner track, then use the spinner in the gear hole to make what remains of the mirror of twilight emerge from the roof.
The guardians of the mirror will tell you its history and show you a scene in which the true enemy of Hyrule, Ganondorf, was transported to another realm by the ancient object. Zant has now broken the mirror, and three of its pieces are scattered over the land.