To reach the final dungeon, you need the Roc's Cape to go to the Temple Remains, then go to Subrosia and make the volcanoes explode. In the lava-flooded Temple Remains you can reach Subrosia's Sword and Shield Maze dungeon.
Get a Key
From the entrance, go north, then go east. Use the slingshot to shoot the statue across the gap, then get the key that falls from the ceiling.
Get a Second Key
Exit west from where you got the key, then use the northwest exit. Go north again. Kill all of the Magnesus and go through the north door.
Kill the Zols, then bomb the cracked stones and use the magnetic gloves to pull and push the N magnet onto the Hardhat Beetle to kill it. Get the key that falls from the ceiling.
Get the Compass
Go east from where you killed the Hardhat Beetle with the N magnet. Avoid the Sparks that move around the blocks, and exit east.
Go to the right side of the room and unlock the key block. Go down the stairs.
Make your way past the Ropes and Keese, and go along the narrow paths to reach the exit at the bottom-left corner of the room. Exit south.
In the room with the rollers, watch out for wallmasters that fall from the ceiling. Use the Roc's Cape to jump over the rollers and reach the stairs at the bottom-right corner of the room. Go down.
Descend the ladder and use the Roc's Cape to jump across the platform to the left, being careful to avoid the spinning flames. Exit to the left and use the Roc's Cape to jump across the moving platform. There are flames that jump up on both sides of the moving platform, and a flame that jumps up through the middle of the platform, so avoid those. Go up the ladder on the left.
Jump over the roller and lava to exit south.
Avoid the giant blade traps and the fire keese and go to the top-right corner of the room. Step on the switch to unlock the door. Go to the bottom-right of the room and go through the door.
Go to the top-left of the room and go up the stairs. Go to the top-right of this room and open the chest to get the compass. You can use the Roc's Cape to jump over the spikes.
Get the Dungeon Map
Go downstairs from where you got the compass. Go through the locked door on the right side of the room. Get into the rotating device, then exit north.
Go west, then jump down the ledge and go back through the door that you just unlocked. Use the rotating device again and exit south.
Kill the enemies in here. The owl statue says "a silent watch may be needed." This means that in order to bring the armos statue to life, you have to stand there and do nothing until it wakes up. After you defeat all of the enemies, exit this room and go back in, then don't press any buttons. The armos statue should come to life after a few moments. Go to the bottom-left corner of the room and go up the stairs.
Go east and open the chest to get the Dungeon Map. Important! While you're here, pull the N magnet toward you and walk right. When the N magnet is on the tile below the stairs, switch the polarity to N and go to the right. This should push the magnet up to be in line with the button. Move to the left to put the N magnet on the button. This will make the bridge extend.
Get the Hyper Slingshot
Go west from where you got the dungeon map and go down the stairs. Go east from this room and jump over the lava, then go up the stairs.
If the N magnet is blocking your path, go back to where you got the Dungeon Map and use the magnetic gloves to put the N magnet onto the switch.
Go west from the stairs.
Touch the bottom two armos statues and kill them with the magical boomerang. Then push the bottom block to the side and open the chest to get the Hyper Slingshot. It shoots three seeds instead of just one.
Get a Third Key
Go back east and jump to the bridge, then go down it and use the stairs.
Go north and jump over the ledge. Go west to the next room and get into the rotating device. It should make you go east. Exit east. Open the chest to get a key.
Get a Fourth Key
Go back and use the rotating device, then go up the stairs and exit east. Go down the stairs and use the magnetic gloves to pull yourself to the S magnet on the right side of the room. Exit east.
The owl statue says "icy cores make piercing blades". Go to the right side of the room and use the Hyper Slingshot to activate the three statues at the same time. This makes some stairs appear. Go up.
Bomb the cracked stones while avoiding the Bubbles. On the left side of the room, kill the darknuts and bomb the cracked stones around the chest. Push the bottom block to the side and open the chest to get a key. Go back to the top-right corner of the room and go down the stairs.
Go to the bottom-right of the room and go through the locked door.
Frypolar switches between fire mode (where he shoots columns of fire at you) and ice mode (where he creates ice blades). You can force Frypolar to switch modes by shooting Mystery Seeds at him. First switch him to ice mode and wait for him to create an ice blade (watch for the shadows). Shoot the ice blade with a mystery seed, then shoot ice-mode Frypolar with an ember seed. Then use the Power Bracelet to lift the ice crystal and throw it at fire-mode Frypolar. Repeat this process until Frypolar dies.
Get a Ring
Go into the warp point that Frypolar left behind, then go one screen north. Go to the right side of the room and use the stairs to exit northeast. While on the ledge, shoot the Hyper Slingshot at the three statues to activate them at the same time. A chest appears. Use the Roc's Cape to reach it. Open it to get a ring. When appraised, it becomes the Steadfast Ring, which prevents you from getting knocked back by enemies such as Hardhat Beetles.
Go south from where you got the ring to reach the warp point. Use it to return to Frypolar's room.
Get the Boss Key
Go through the north exit. Light all of the torches with ember seeds to make stairs appear. Go up.
Exit north. To solve the puzzle, you have to push the ice blocks onto the three yellow tiles on the right. To do this, go to the leftmost block and push it down, then right. Then push the topmost block down, then right. Then, push the rightmost block down, right, up, and right. Finally, push the remaining block right. Stairs appear at the top of the room. Go down.
Go down the ladder and carefully jump onto the floating ice blocks. Try to jump as soon as you land on each block; otherwise you'll slide right off and get hurt by the blade traps below. Use the Roc's Cape to float over to the final ledge. Go west.
Get on a conveyor belt that comes close to you and be careful to stay on it. Then jump onto the next conveyor belt, and jump to the upper left ledge when possible. Exit west from the upper level.
Jump onto the first spiked thwomp, being careful not to jump too far and miss it when it falls. Wait for it to go back up, then jump onto the second thwomp. Wait for it to go up, then jump to the ladder on the left. Go up.
Go to the bottom-right of the room and step on the switch to extend the bridge. Then exit east.
Use the Roc's Cape to jump over the blade traps that keep spinning around this room. Exit east.
Go to the top-right of this room and use the Magical Boomerang to hit the crystal switch in the bottom-middle of the area. Cross the bridge and exit south.
Don't bother with the switch in the middle of the room. It just opens the southeast door, which leads to a Ball and Chain soldier. Killing it does nothing. Instead. Just kill all of the keese and the Pols Voices (use bombs on those) to open the southwest door. Go through. Go up the stairs and open the chest to get the Boss Key.
Get a Fifth Key
From where you got the boss key, exit south. Jump down the ledge to the ice cube room. Unlock the west door and exit west.
Go through the room with the sparks and exit west. The owl statue says "The magical ice freezes all."
Bomb the wall next to the owl statue and exit north. A ghostly Armos statue will move around the area. Try to memorize its path. Then walk the same path as the statue. It takes a different path each time you enter the room, so if you get it wrong, exit and try again. A key will fall from the ceiling when you do it correctly. Get it and exit south.
Get a Sixth Key
Pick up an ice crystal and exit south. Throw the crystal into the red square in the bottom-right of the room. This solidifies some of the lava in the room below. Go down the stairs. Go to the right side of this area and open the chest to get a key.
Exit west from the area where you got the key. Go to the far left side and open the chest to get bombs.
Get a Seventh Key
Go east from the bombs, past the stairs. Exit east. Then go up the stairs in this area where you got a key earlier. Exit north.
Pick up an ice crystal and get into the mine cart. When it drops you off, put the ice down (it doesn't break when you drop it), then unlock the key block above and throw the ice crystal into the hole.
Don't hit the switch. Get back into the mine cart and ride it back to the room with the ice crystals. Pick one up and get into the mine cart again. Then put down the crystal, hit the switch, pick up the crystal and get back into the cart. Throw the crystal into the hole.
Get back into the mine cart. Hit the switch, and ride the mine cart to the ice crystal room again. Pick one up and ride the cart. Then put the crystal down, unlock the south door, pick the crystal up and go through. Get in the mine cart here. Throw the crystal into the hole. Go down the stairs in the bottom-right corner of the room.
Go east, then north. Go to the stairs to the right and go up. Follow the path around and open the chest to get a key.
Reach the Boss Door
Go back the way you came until you reach the lava room. Go south, west, north, and keep going north until you reach the top of the room. Unlock the key block and go east, and unlock the boss door and go through.
Stun Medusa Head with Pegasus Seeds and hit it with your sword. Jump over the blue orbs that it spits out to avoid getting turned to stone. It always looks up with its mouth open and turns yellow for a moment before spitting the blue orbs, so get your Roc's Cape ready and be prepared to jump and hover until the blue orbs have stopped. Medusa Head may also go to the top of the room and shoot lasers from its eyes. You can jump over these with the Roc's Cape as well.
Get the Essence
Exit north and go up to the altar to get the final essence, the Changing Seasons. Outside, the Maku Tree says that he has something to give you. Go south twice and use the portal. Go outside and use a Gale Seed to go to Horon Village. Go north, east, and north twice to reach the Maku Tree. He gives you a Huge Maku Seed, which grants you access to Onox's Castle.