Right away you see a tile to speak to Sahasrahla. He warns you that you should bring green potion into this dungeon. He's right; if you don't have green potion, go get some! One or two bottles should do. Get it for free from the Waterfall of Wishing.
If you're ready to proceed, pick up the skulls for a full magic jar and a bomb. At the question mark above you, use the Cane of Somaria to create a platform. Step onto it and it will move north along the line to the top of the room. Exit north.
More question marks. Create a platform, step onto it and press right to go in that direction. You stop at the next question mark, but you don't want to go in this door. Press up to go up to the next question mark, and go through the door.
This next part is tricky. Create a new platform at the question mark, then pick up the pots below for a heart and large magic jar. You need to light all four torches with the Fire Rod to open the door above. Read this before you proceed so you can memorize the order: Step onto the platform and press down, then, when you're between the bottom two torches, light the torch to your right. After you loop around, when you're between the top two torches, light the torch to your right. Finally, quickly, when you are above the left-hand torches, fire straight down with the Fire Rod to light both of them. Once you've done that, rush through the north door that is now open.
Orange, spiky things are rolling up and down the room. Get past them by moving to the side when it passes. At the top of the room, get the map and a small key. (The skull hides a small magic jar.) Then exit the way you came in. Exit west to the big question mark-filled room.
Create a new platform, then go north, then west until you reach a locked door. Go through.
Zols will appear underneath you; walk out of the way and kill them. You have to kill the orange, bouncing caterpillar to get the key. Be careful; each time you hit it, one of its body segments will come flying out and bounce around the room. Don't get hit by it. You can kill the body segments after they start bouncing around. Once it's gone, collect the key and exit north.
Stand in the doorframe; the Chain Chomps can't get you there. If they hit you, you lose three hearts, so take caution. From the bottom of the room, hit a crystal switch with your boomerang so you're below the orange barrier. Then push the left-hand top block (next to the blue line) to the side to make a chest appear. Use the boomerang to hit the crystal switch and lower the orange blocks once more, and open the chest for a small key. Go north through the locked door and down the stairs.
Use Magic Powder on the Bubbles to get fairies, to replenish the hearts you lost to the Chain Chomps. Head east from the stairs, then south down the narrow passage (there is an orange, bouncing caterpillar here) to find stairs leading up to a sort of pipe. Go up the stairs and into the pipe, and you automatically go through the pipe to the northwest corner of this room.
Exit to the next room, where there is lava below, and more pipes. Take the lower pipe and exit to the next room. Quickly run down in front of the Bubbles and go below to where there is a crystal switch. Hit it, then go below, run to safety from the bubbles, and you have no choice but to get hit by the yellow swirly thing. DON'T face the locked door to the right; an eye above it will shoot lasers at you if you do. Once you're back in human form, kill the orange caterpillar for the key. CAREFULLY unlock the door and run away FAST so you don't get hit by the laser. To get through the door without getting hit by the laser, face west and hold B so you're holding your sword out. You'll walk backwards, so walk through the door, back to the lava room.
Enter the pipe to find yourself at a chest containing the Big Key! Enter the next couple of pipes until you're back in the first pipe room. Pick up the skull for a large magic jar, then drop off the edge and go back south, up the stairs that took you to the first pipe. Go through that pipe, back to the lava room.
This time, take the upper pipe. Exit to the next room. The bottom-right skull hides a swirling yellow thing, so don't pick it up. Avoiding the fireballs, kill the two bouncing caterpillars one-by-one, watching out for their flying body segments, to open the doors. Use the south door, then the west door.
In here, there are five laser eyes. The first, third, and fifth will only shoot lasers if you're facing them (they're the closed ones). The other two will shoot lasers at you no matter where you're facing. Lift the closest skull, then go down below to the cracked wall. Walk quickly past the fourth laser eye to set a bomb by the cracked wall, then quickly walk to a corner, out of the blast zone and away from the eyes. When the bomb breaks the wall open, quickly go outside.
There is a piece of heart that you can only get from right here, during the Turtle Rock dungeon. Don't miss it! Go to the far right edge of the ledge and use the Magic Mirror. In the Light World, go into the cave entrance. Four Goriyas are sitting there waiting for you to come in. To get the ones on the right, grab hold of the barrier separating them from you, and move the controller so that the Goriya comes right up to you, then hit it with your sword. One hit with the Golden Sword should kill it. Then go up and pound down the pink things to kill the top two Goriyas. The door will open, leading to a chest on a lovely blue altar that holds the very last piece of heart.
Go back outside and step in the warp to get back to the Turtle Rock dungeon. Go through the door above.
To conserve magic, use your hookshot on the big chest to get across the gap, rather than using the Cane of Somaria. Open the chest for this dungeon's treasure: the Mirror Shield! This shield is so big that it's a wonder Link can see over the top of it at all. Now you can deflect the lasers that those evil eyes shoot at you! Go north through the door. Avoid the fireballs and the orange spiky thing and go through the Big Key door above. In the lava room, go into the pipe, and into the next room.
Just ignore the orange caterpillar, it's easy enough to avoid. Dash into the north wall (a bomb is not necessary). (The right wall leads to some items and a lot of blue rupees; I won't tell you how to get them.) Be careful of the little black things that scurry out of the north hole, and go through.
When the rolling spiky thing is at the right, go up past the first orange line and quickly use your boomerang to hit the crystal switch, and quickly run to the chest to the left for a small key. Once you have it, follow the roller towards the right and use the boomerang to hit the crystal switch again, then run up and go through the locked door, down the stairs.
The next room has an extremely complicated question mark maze that you have to get through, all in the dark. First, to get to the central platform where you have to hit a switch, wait until you see the spinning flames below and head south, then east, then keep pressing down to reach the platform. Lift the skull and press the switch, which will stay down. Then get back on the platform and at the junction head east. Keep pressing right until can't go any further east, and then press down until you can't go any further south. Finally keep pressing left until you are at the southern platform and out of the room.
Dash south through this room carefully, then as soon as you pass the Hiploop stop dashing so you don't fall off the edge. Exit south.
To avoid the laser eyes in here, make sure to hold down the B button so your shield is on the correct side to protect you from the lasers. You can get the top three chests if you want; they just hold rupees. Get rid of the pink Hardhat Beetle below and get the final chest for a small key. Get out of the way of this laser and dash north to the last room, then go through the locked door.
Use Magic Powder on the Bubble to turn it into a fairy to restore your health; you probably got hit by spinning flames in the dark maze room. Speaking of maze rooms, you're now in a blue/orange block maze. Go past the two orange lines and hit the crystal switch with your boomerang. Go left past one blue line and hit the switch above. Go north as far as you can and hit the crystal switch, and it's a clear shot to the north wall, where there are stairs leading down.
Before picking up the skulls, create a platform with the Cane of Somaria. Then get the skulls for a heart and a large magic jar. Walk onto the platform to go north across the bottomless pit, and you reach the boss door! Go inside to meet...
-- Trinexx --
This boss has three heads, one brown like its body, one red, and one blue. The brown one will occasionally shoot right out at you, so watch for Trinexx's tail to wag faster, then try to run so you don't get hit by its brown head. The red head spits fire and is vulnerable to the Ice Rod. The blue head creates ice and is vulnerable to the Fire Rod. Since the blue head creates ice on the floor that never disappears, you should kill it first. Use the Fire Rod on the blue head to stun it. Hit it three times, stunning it again if necessary. Then go over to the red head and stun it with the Ice Rod, repeating the process you used on the blue head. When the two heads are dead, Trinexx appears to be defeated, but it's not. Its large, rocky shell explodes and it turns into a rock worm. Its middle segment glows; that's what you need to hit. It really chases after you, so keep running. Hit the glowing segment three times, and it dies. The heart container appears in the middle of the room this time, instead of inside the explosion, so stand there to get it (it's the last one!) and catch the crystal that holds Princess Zelda!
She confirms that you are indeed the legendary Hero; she says she knew it all along. Ganon is in his tower, waiting to pass through the gate into the Light World. If he makes it to the Light World, he will be unstoppable; while he remains in the Dark World, he can't escape you. Zelda says to go to Ganon's Tower, where the maidens will break the barrier. You are returned to the outside of the dungeon with hearts and magic filled!