Task 1: Getting the First Key Shard
Pillars of Flame
In the very first room, time your jumps so that you get to the next ledge without the lava geysers hitting you. Proceed north into the next room, where you will have to break wooden barriers with your sword. There are pillars of flame, where you have to stand on a switch with your iron boots on to deactivate them and run past them. When you reach the second flame pillar, step on the switch with your iron boots, run past the now-deactivated pillar, and make a u-turn while on the platform to climb a ladder. Run across the top to the east side of the room, hit another switch to the far south, and head north, and take a right turn past the pillar while it is still deactivated. When you reach the door at the north end, it is blocked by a gate. Jump onto the tall platform next to it, then equip the iron boots to lower the platform and open the gate, revealing the door.
The Key Down Under
When you enter the roundish chamber, there will be a cutscene showing a magnet up above. Instead of heading to it, go downwards instead and open the chest for a small key. Head over to the east side of the chamber, and use the key to move on. Defeat the Dodongos by hitting their vulnerable tails.
Chains, Magnets, and a Key Shard
In the chamber to the east of the roundish one, pull the chain attached to a section of wall in the northeastern corner (take out the enemies first). After you pull it all the way back and let go, jump from platform to platform until you reach the passage previously blocked by the wall you moved. If you get through before the wall slides back in place, you'll be able to continue onward. If not, pull the chain again and hope for better luck this time.
In the room flooded with water, jump in and equip your iron boots to sink to the bottom (watch the blue oxygen meter underneath your health), and walk to the switch on the floor, which activates a magnet up above. The magnet will pull you up when you are beneath it and have the iron boots on. Walk along the ceiling to reach the door, then proceed onward.
The next room houses the elder Gor Amoto, who tells you that the big key is in three pieces, and gives you one of the three. You need to find the remaining two elders to complete the key. Behind Gor Amoto, you'll discover a chest that holds the map and one with 20 rupees. Climb the ladder and pick up the shaking pot to uncover Ooccoo, your handy warping friend.
Task 2: Getting the Hero's Bow and Big Key
Return to the large roundish chamber, picking up piece of heart #7 on the way if you want to (take the upper exit from Gor Amoto's room). When in the chamber, run to the platform in the middle and defeat the Torch Slugs infesting it. After they're gone, use the iron boots activate a switch and a moving magnet that carries you over the lava.
The flooded passage to the north of the roundish room contains Tektites and a small key. Destroy the Tektites, then equip the iron boots by the chest and sink down to it for the key. Then swim to the southeast section of the pool, sink to the bottom, push a crate out of the way, walk into the wire cage, and resurface before you run out of air.
Wearing your iron boots, stomp on the platform at the east end of the room to activate a magnet. Use the magnet and a magnetic path to get to the room's highest platform. Walk to the center, hit another switch, and drop down into the magnetic field. It will pull you to the west wall, where you'll walk up to a platform containing rupees and a blue crystal switch. Hit the crystal to open the gate at the north end of the room.
Drawbridges and Archers
Walk to the east side of the chamber that houses two Beamos and a drawbridge, and walk up the magnetic path. You can take the right fork to get to piece of heart #8, then take the left fork in the path and cut the drawbridge rope with your sword to proceed onward.
In the large northern chamber, you are outdoors and there are archers to avoid. Run to the area of this room that has the Beamos and collect a small key in a chest. With the key, follow the path west to unlock a door, then continue onward. In this room, when you can take a right to go to the beamos and key, or left to open the door. jump down. there is a chest with a purple rupee in it. (50)
A long platform revolves at a steady rate. One side contains three magnetic patches, and the other just one. Use either side as you progress across it, using the iron boots on a magnetic patch when it turns over.
Gor Ebizo, the second elder, will greet you in the next room. He will give you the second key shard. Collect 10 rupees from a chest, climb a ladder, and follow a path to the upper portion of the room you were just in. Turn to the right and use your boots to walk a magnetic path to the door on the south side.
The round western room houses a magnetized platform and a Goron with armor and an attitude. Walk towards the other side of the room. This triggers a cutscene where Dangoro sees you, and tells you no-one is allowed to pass. The battle starts.
Get close to Dangoro, take a few swipes, and attack his belly when he raises his arms. After a few hits, he will roll into a ball. Put on your iron boots, face him, and wait for Dangoro to approach. Press to grab him when he gets close, and toss him left or right over the edge.
When you've thrown him into the lava three times, he gives up and lets you pass. Head south into the next chamber, grab the bow, and use it to shoot the rope that holds up the drawbridge.
The Final Key Shard
Continuing south, you'll enter a room filled with Beamos. Hit the red light with an arrow to destroy them. Knock out every Beamos in the room, then pull them back to uncover, among other things, the compass and the door in alcoves. Enter the room to the west of the Beamos chamber to discover the final goron elder and key shard. Collect a 50 rupee prize, then return to the Beamos room and head south.
Roll into the wire fence with iron boots to knock it over, then use your bow to hit the enemies nesting on stalactites before hopping from island to island. When you get to the gate at the north end of the room, you'll find a switch that takes you to the ceiling, where a Dodongo waits. To make the battle much easier, destroy it from below with your bow. Hit the crystal from the ceiling with an arrow, then drop to the floor and advance east.
You'll find yourself on the upper level of the roundish room. Cut down a drawbridge to the north and trigger a magnet crane that will carry you to the north end. Drop down and head north. You're back in the room with the archers, but this time, you can pick them off. Use your bow to destroy the archers and Beamos in sight, then advance to the east side of the room, where you can destroy two more archers. Trigger another magnet crane, drop onto a platform, and let the crane sweep you up. Slice the drawbridge rope with an arrow while hanging upside down, then drop onto it and move on into the next chamber (or pick up a fairy in the northeast corner if you feel you need it).
In the next chamber, pick off the remaining archers and cut a drawbridge to access the boss chamber. Go in when you are ready.
Twilit Igniter: Fyrus
When you enter, the room is dark. Fyrus is in the middle of the room, chained to the floor and ceiling. A jewel on his head turns red, and he awakens. Then the battle begins.
After you get control of yourself, use the bow to hit the glowing eye on his forehead (it is too far away to target it, so you'll have to aim manually). After you score a hit, Fyrus will walk around dazed. Run behind him and grab one of his chains, put on the iron boots, and pull the chain to make him fall down. Run up to his weak spot (the pink spot on his head) and slash it with your sword. The beast will revive itself after about three hits, so repeat the process until it kicks the bucket. If you have trouble dragging it down with the chain, you can knock it down by hitting its eye with enough arrows.
After you repeat the process three times, Fyrus hold his head in pain, before turning back to his origional form, Darbus. You will receive a heart container and a fused shadow. Midna gives you the name of the Twilight King: Zant.