The journey to the Great Palace is long and difficult. Before you go, make sure that you have put all of the crystals in place. To check this, press pause and make sure that there is a 0 next to the crystal symbol on the bottom left of the screen. Otherwise, the Great Palace won't unlock for you.
Also, be sure to level up all of your attributes to 8. If there are any P-Bags that you didn't collect, you should go around and do that now. You can also pick up any 1-Up Link dolls that you didn't get before. For an easy way to level up, go back to the Ocean Palace. There is a room with falling blocks and an orange Moa. If you stand three blocks up, you should be able to fight infinite Moas, which will quickly give you points. Read the Ocean Palace section for more information.
Get Thunder Spell
There is one more thing that you have to do before you go to the Great Palace. That is to go to Old Kasuto. If you're coming from the Hidden Palace, go west from the desert and go across the bridge. The town here is Old Kasuto.
Now that you have the Cross, you can see blue Moas floating around. These were invisible before you had the Cross. Go into the house in the first screen and you will find an old man. He will give you the Thunder spell. You will need this spell in order to beat the game.
Now it's time to go to the Great Palace. Remember: if you haven't put all of the crystals in place, the Great Palace won't unlock for you.
To get to the Great Palace, go east from Old Kasuto across the bridge, north from the desert and west across the bridge. Then run south through the graveyard. You might want to run onto a graveyard square to make enemies appear but then run right back to the path to avoid the enemy encounter, then run south.
There is an action screen right before you step onto the darker part of the ground. There are Moas and Lizalfos behind the fence throwing rocks at you. After you get past this, continue west. There will be another action screen, this time in a cave. You must cast the Jump spell to get over the lava pit. Be very careful to avoid the floating eyes and the Moas. There is a Lizalfos beyond the lava pit.
Past the cave, go north. The path splits with a small area to the left. The leftmost walkable square is an action screen with a 200 point P-Bag in it. Go north from here to encounter another action screen. It is the same as the previous one, with a lava pit that you must use Jump to get across, and a Lizalfos and some floating eyes and Moas.
Continue going north into the cave. Carefully avoid the eyeballs and Moas. In the next screen you will need to cast Fire if you want to kill the scorpion. There is a Lizalfos here, too.
Outside, the path is straightforward, so continue on. There is an action screen that is the same as before, where you must cast Jump to get over the lava, and you have to kill Lizalfos to get through.
Finally you will reach a cave that contains some Lizalfos. Once you get out of the cave, you have reached the Great Palace.
Once you go into the Great Palace, if you get a game over and choose Continue, you will start over at the Great Palace. However, if you choose Save, you will start at the North Palace.
The Great Palace has a bunch of dead ends and wrong ways. I won't mention those areas unless there is something really useful there, like a fairy or a red magic jar.
When you arrive at the Great Palace, go to the right to make the magic barrier disappear. If it doesn't disappear, it means that you didn't put all of the crystals in place in the palaces, and you will unfortunately need to go back and figure out which palace you didn't complete.
After the magic barrier is open, go down the elevator. From the entrance elevator, go to the left. The right is a dead end. You will encounter a Fire Hawk on the steps. This monster jumps around and spits flames. Sometimes the flames jump toward you, so be careful.
In the next room there are some breakable bricks, but beyond the bricks is a dead end with a few Bots. Jump up the bricks to the upper level, but be sure to jump after you pass the column, because there is a hidden gap in the floor. Once you get past that, go down the elevator.
Once you have gone down this second elevator, go to the right. The left takes you on a long, pointless journey to nowhere. When you go right, you will pass some columns, and a bridge over lava where there are no monsters at all.
In the next room, there are a couple of columns, followed by a Fire Hawk at the end of the room. The statue up above doesn't give you a red jar, so just go down the elevator.
Down below, a bunch of golden floating statue heads (which can fly higher and lower) will fly toward you. There are two areas of bricks that you need to break through to get through this room.
In the next room, a red Fire Hawk soldier will be jumping around using his sword. After that, a blue Bot is on the stairs. You will need to down thrust through the blocks to get to the elevator.
If you go down one floor then walk through the wall to the left, the statue has either a red magic jar or a red Fire Hawk soldier. Once you get that, go back to the elevator, skip the next floor to go down to the bottom floor that this elevator goes to.
The correct path is to the RIGHT from this elevator. If you go to the left, it will take you the wrong way and it will take a long time to get back on the correct path.
Going right from this elevator, you will encounter a Fire Hawk. Beyond that, there will be a room with short columns and a couple of red, fire-spitting Ropes, as well as some golden floating statue heads flying toward you. The statue at the end of the room might give you a red magic jar. Go down the elevator at the end of the room.
The next room has some brick walls with Bots inside. There is a blue Fire Hawk soldier who throws swords like a blue Iron Knuckle, but it jumps.
The next room has a crumbling bridge with a red, fire-spitting Rope on it. Beyond that, there is a Bubble under a ledge. Go down the elevator at the end of the room.
The next room has some blue curtains on the ceiling but doesn't have a miniboss or anything. There is a giant Bubble and a Fire Hawk. After that you will encounter a jumping blue Fire Hawk soldier who throws swords, and a giant Bubble on the stairs. Use the down thrust to break through the blocks at the end of the room, and go down the elevator.
Walk through the left wall to find a statue that might give you a red magic jar. Return to the elevator and go down one floor. If you go to the right from here, there are some blocks that you can break through to reach a fairy that will heal you up, but you need to be careful to stop downthrusting or you will break through and fall in the lava. To the left from the elevator on this floor, there is a room with a bunch of Bots and lava pits, beyond which is a room with a 1-Up Link doll. Go back to the elevator and go down one more floor.
Don't go to the right. It's a dead end. Instead, go to the left. There is a Bot and a Fire Hawk on the steps.
In the next room, you are in a lower area where some golden floating statue heads will fly toward you. Break through the bricks near the left side. The fifth and sixth bricks from the left cover an invisible hole in the ground. Drop down that hole.
You're getting close to the final boss now! Go to the right, and a Giant Bot will fall from above. Do an upward thrust to break it into a bunch of small Bots. Try running past before they fall on you.
In the next room, there is a crumbling bridge over lava with some Myus on it and a couple of Bubbles under the bridge. There is also a hole under the bridge, just past the middle. You need to drop down the hole. You COULD go to the rooms on the right, because there is a fairy at the end, but it's probably not worth it, because you will soon have access to two red magic jars. However, those jars disappear after you take them. It's up to you. Just keep in mind that if you go to the right, you will pass through a room with a bridge and some fire-breathing Bago-Bagos, followed by a room with a couple of giant Bubbles where the fairy is. So I recommend falling down the hole under the bridge now instead of trying to get that fairy. When aiming for the hole under the bridge, be very careful not to fall into the lava.
Once you fall down, you can go to the left and break through the bricks. There are two spots where you can find a red magic jar or a red Fire Hawk soldier. Just break through the bricks at Link's eye level when he's standing on the floor. But be careful because they might spit out red Fire Hawks. If they do, just run out of the room and try again. Note: These magic jars will not reappear after you take them.
When you're sufficiently healed up, go to the right. You are about to fight the final boss, so get ready! You will reach a room with columns and a blue platform. Once you walk far enough to the right, the Thunderbird will appear.
At first, the Thunderbird is red. In this state, it can't be hurt by anything. You have to cast Thunder to make the Thunderbird turn blue. Once it's blue, you can hit it in the face to hurt it. It's pretty tough to avoid the fireballs, so cast Reflect to protect yourself from some of it. And cast Shield to give yourself more protection.
There's kind of a cheating strategy that you can use against Thunderbird. Just stay in the far right corner of the screen. The fireballs can't hurt you when you stand there. You will have to move toward the left when Thunderbird is floating downward because you can't hit Thunderbird's face when it's off screen. You have to move to the left to lure it over so its face will be accessible for you to hit it.
Once you have killed Thunderbird, go to the next room. The old man is there with the Triforce of Courage, but there is one final test for you. You must fight the evil within your own heart in order to become worthy of the Triforce. Dark Link will split off from you.
Cast Shield. If Dark Link is just standing there, you need to get closer to it to make it come over to you. An easy way to defeat Dark Link is to stand on the far left side of the room and just swing your sword repeatedly whenever Dark Link comes close. If you're lucky, Dark Link will not be close enough to do a downthrust and you will just knock him back.
Once Dark Link is defeated, you obtain the Triforce and can watch the ending. Congratulations!