The seventh Dark World dungeon is surrounded by cliffs on all sides. This page explains how to enter the area.
Leave the Ice Palace
From the entrance of the Ice Palace, use the Magic Mirror to go back to the Light World. If you are transported into a bush or a rock, adjust your position before you use the Magic Mirror so you arrive on safe ground.
Refill Magic
Once you are in the Light World, if you don't have any Medicine of Magic in a bottle, it is recommended to get some, so play the Flute and go to 2, the Witch's Hut. Go northeast to the Waterfall of Wishing and throw in an empty bottle to get Medicine of Magic.
Reach the Dark World Swamp
Go outside and play the Flute and go to 6, the Desert of Mystery. You will arrive on a previously inaccessible ledge overlooking the desert where there are two black stones. Pick up the stone on the right to reveal a warp tile. Step on it to arrive in the Swamp of Evil.
Get a Piece of Heart
Jump down from the ledge and go north while staying near the west wall. Watch out for the Dacto that flies at you, and beware of the Swamolas and the orb-spitting Kus. When you reach the northwest corner of the area, you find an opening in a plant-like face. Go into it.
Wait for the two Sparks to go past, then go north and down the stairs to find a block puzzle. See the diagram below for instructions, or follow these directions: Push the bottom-right block to the right to reach the rightmost chest, which contains 20 rupees. Then push the bottom-left block to the left, the one above you up, then go to the right side of the block below the left chest and push the block left to reach the chest, which contains a Piece of Heart.
Get a Second Piece of Heart
Go back outside and go north to the north wall of the area, then go east to reach the northeast corner of the swamp. Go as far east in the northeast corner as you can go, then use the Magic Mirror to go back to the Light World. Pick up and throw the large boulder, then go down the stairs.
Push the blocks until you can reach the Piece of Heart. You can leave and come back if you need to reset the blocks to their original positions.
Enter the Dungeon
Go back outside and step into the sparkling spot to return to the Dark World. If you end up in the wall, just keep repositioning yourself in the sparkling spot until you are back in the swamp. Go west from there and you will see another plant-like face with an open mouth. You can optionally go in to use the Fairy Fountain there to heal up. From there, go west and you will see a platform. Go south until you can reach the walkway leading north onto the platform. Go to the north end of the platform and you will see a lightning symbol. Stand on that symbol and use the Ether Medallion. The dungeon entrance will open. Go through to enter Misery Mire.