NOTE: This Walkthrough will cover, each and every Heart Piece, Item, Boss, and everything else.
Once outside Misery Mire. Use your mirror to get to the Light World. Use the flute and head on over to the location at the middle-bottom, which is location 7. Head right one screen, up a screen, and then head left at the top-left part of the screen. Pound the stakes here and lift the rock there to reveal a portal. Head through it to get to the Dark World. Pound the stakes and head right a screen. Head up a screen here and go into the building here which was where Links House was in the Light World.
Buy the super bomb on the left. It costs a 100 rupees. Afterworsd exit the building. The bomb will follow Link around. You cannot jump off cliffs or dash when it is following you or it will start the detonater. If you accidentally do so, just walk up to it and it should start following you again. head right a screen, and then pound the stakes and head up a screen. Head left a screen to get back by the pyramid. Head up the stairs and to the left a little bit.
You will see a wall with a weird looking object on it. Leave the super bomb here and walk to the side and wait for it to explode. It will reveal a hidden cave. Enter it.
There is another mysterious pond here. It will ask you to throw in item in. Throw in your Bow and Arrows and wait for the Fat Fairy to come out. When she asks if you threw the item in, say yes and she will give you something better in return, the Silver Arrows!
Walk away for a few seconds and then walk back to the pond and once again it will ask you to throw an item in. This time throw in your tempered sword. Once again say that you threw the item in and in return you will get the Golden Sword.
Once again step away from the pond and then walk there again. This time when it asks you to throw an item in, throw in a bottle and in return you will get a bottle filled with green potion. Afterwards leave the cave. Use your mirror to get to the Light World. Then use your flute and go over to location 1 on top of Death Mountain. Head all the way right a screen. Use your hookshoot to get accorss the broken bridge here.
Head right and down. You will see a black rock down there. Lift it to reveal a portal. Go through it to get to the Dark World. Head up and right until you are at the top-right of this area. There are two caves here, head through the one on the left. Head left and up the stairs. Head up and fall down the hole. Push the block on the left up and head up the stairs. Head right and fall down the hole here. Head right and up the stairs. Head all the way to the bottom and fall down the hole there.
Move the blocks how they are arranged in the picture and open both chests for some rupees and some bombs. Head left and up the stairs here. Head down and out of the cave. From the exit lift the rock just to the left here and go into the cave.
You can hookshot your way through the left side of this room if you would like some rupees. There are four treasure chests here, each holding 50 rupees. Afterwards get back on the platform where you first entered.
Head up a little past the edge of the platform. It looks like you should fall but there actually is a platform here. Use ether to make the platform visible. Make your way up. Place a bomb and head up a screen. You can bomb the top wall to get to a fairy that will restore your health. You can also bomb the left wall. Bomb the left one and go through. You can bomb the upper wall to get catch some fairies if you would like. Afterwards exit to the bottom.
Once outside, use your magic mirror and you will be able to get a quarter heart piece that is waiting for you. Grab it and go back through the portal. There is spot at the bottom of this rock where you can jump down. Do so and then head right and up and exit right a screen.
Use your magic mirror again to get back to the Light World. Head to the bottom and lift the big rock here. Walk up and hit the stakes in the following order... Right, Top, Left. It will reveal a portal so go through it.
You are now on top of Turtle Rock. The entrance is just below you. There is a symbol of quake right there. Use Quake and you will reveal the entrance to Turtle Rock. Jump down. If you want some rupees, you can pull on each of the Turtles two arms to get 40 rupees. Enter Turtle Rock.
Once you enter the room head up and use your Cane of Somaria on the question mark to create a platform. Walk on it and ride it up. Head up a screen. Once again here, use the cane of somaria and get on the platform. Ride left and take the first door down.
Walk down and grab the compass from the chest. To get out of this room. Face down and hold your sword like you are going to do a spin attack and walk up. The eye wont shoot at you and the door will remain open. Creat another platform and ride it to the top-right. Go through the door on the right side of the room.
This is one of the most difficult rooms in the game. Make a platform and get on it and start by going down. Let it go down right, around and up. Get your firered out. Let it go all the way left, down and right. As it starts going up use your firerod to lite the bottom-right torch. As it continues to go up lite the top-right torch. Once it turns left and you are directly above the two torches on the left use your fire rod to lite them both. The door will open. Once your platform docks. Quickly run up through the door.
This room is pretty fun to go through. Stay against the walls and make your way up the room slowly avoiding the moving spikes. Grab the Map in the left treasure chest.
Grab the small key from the chest on the right and then head back down through this room and exit down. Head left again. Create and get on the platform here. Ride it to the top-left and go through the locked door.
Kill the bumper guy here and then grab the key he leaves. Head up through the locked door.
Hit the orb at the top so that you can move the block that is moved on the picture. It will reveal a treasure chest at the top in the middle. Hit the orb and open the chest to get a small key and then head through the locked door and down the stairs.
Head to the bottom-right of the screen and up the stairs. Go through the pipe and exit through the door. Take the bottom pipe here and go through the door. Kill the bumper and grab the small key and go through the locked door.
Go through the pipe and and open the chest for the Big Key. Go through the bottom pipe and through the door. Head through the pipe and jump down. Go back to the bottom-right here and through the pipe. Go through the door once again. This time go through the pipe at the top. Afterwards go through the door.
Kill the two bumpers here and then head down a screen. Go through the door on the left. This room could be a little difficult. First run down and throw a bomp at the bottom wall to reveal a hole that leads outside. Now run to get outside. Head across the platform. Before going through the door here, use the mirror right in front of it. In the light world go through this door. Kill the four enemies with your sword and bombs if needed to open the door at the top. Go through it and open the chest for the 24th and final heart container.
Head back down a room and exit the cave. Go back through the portal to get back to the dark world and then go through the door in the Dark World. You can use either the Cane of Somaria or a Hookshot to get across and then open the Big Chest to get the Mirror Shield. Head up a screen. Head up through the locked door and then take the pipe. Head up a screen.
Bomb the right wall and go through. Kill all the enemies here and then push the top block to the left. Pull the left tongue and go up a screen. Walk up and grab all the rupees in this room. Head back down and then left a room. Bomb the upper wall and go up a screen.
Hit the orb and go and open the chest to get a small key. Make your way back right and hit the orb to go up through the locked door and down the stairs. This is one of the hardest rooms in the game. Use the Cane of Somaria to make a paltform and then get on it.
Try making your way to the middle platform. There are several different routes you can take and it is hard to explain in detail. This could be very aggravating but you will eventually get it. Step on the switch once and then get back on the platform. This is even harder, but make your way to the door at the bottom left. Head down a screen. Run down and head down a screen.
Head all the way to the bottom here and place a bomb on the bottom wall. Head outside and then right back in. Make your way to the chest at the very bottom. The Mirror Shield should keep you well defended against the lasers. Once you get the key, use your mirror to get to right where you just re-enetered the dungeon. Head up a screen and then head left through the locked door.
Make your way through this room by hitting the orbs and moving up. Killing the anti-fairies to get full health is a good idea. Head down the stairs at the top. Create a platform here and ride it up to the top. Head up a screen to enter the boss room. Trinexx is waiting for you. There are two stages to this boss as well. The first stage consist of the two heads on the two sides of him. Fire kills the ice head and Ice kills the fire head. Kill the ice head usuing the fire rod. After using the fire rod, it will get stunned giving you time to strike it with your sword. A couple shots with sword should kill him. Freeze the Fire head with the Ice Rod and then use your sword to kill it.
After the two side heads are defeated. The big turtles armor will fall apart and he will start to move around the room. Part of the middle of his body is glowing. Strike it with your sword a couple times and he will be defeated.
Grab the Full Heart Container.
Also grab the 7th and final crystal and then listen to Princess Zelda talk to you about Ganon and the how she knew that you were the Legendary Hero all along. She tells Link that Ganon is waiting for you at Ganons Tower. May the Way of the Hero Lead to the Triforce!