-| AFTER LEVEL 9 |-
Well, now you know what the spoiler alert thing is about. Level 9 is not the end of the game. I figured it'd be nice to have a surprise new level at the end, so please don't post anything about it on the forums or chat or wherever. All questions will be answered here.
Level 9 3rd Floor:
Well, this is really simple. Take a look where the compass is pointing. It's off the map, north of where you fought Ganon.
All you need to do is avoid Zelda completely, she is a trap set by Ganon, and will quickly kill you. Instead, walk north through the wall, and you will find yourself on a path of lighter tiles.
Follow this path west, and there will be a portal waiting for you. Take this portal and you will be transported back to the overworld, on top of a wall in North Castle.
Go along the wall south and east, and you will trigger a set of ladders, and a new portal. The ladder leading down the wall is where that little one tile outcrop is in the water (I'm sure you wondered what that was doing there) so you can get to the portal easily. The portal will bring you to the Dark World.
Dark World:
Dark World Map
The dark world is an annoyingly colored overworld section. Don't worry, it isn't very large. And you can use the portal at the beginning to go back to North Castle in case you need to stock up on potions.
There are two paths to choose at the beginning. The left side is full of rock while the right is full of bushes. They're both pretty much the same, and lead to the same place, so it doesn't matter which you pick.
You will come across some of Ganon's strongest forces here, but keep in mind that you don't have to kill anything. You can just run through, but pause when you get to the part where the rock and bush sections come back together (it will be obvious).
If you push the rock that is closest to the center of the screen, you will find the last fairy spring in the game. Fill up your hearts here if you need to, or you can just skip it.
From there head north between the walls with tons of statues shooting fireballs at you (reminiscent of the end of Zelda 2?). You will come across a glowing palace, the real last level of the game.
Dark World Palace - Ganon's Hideout:
Ganon's Hideout Map
This dungeon isn't very complicated. It's not as large as most of the triforce dungeons, and there aren't multiple floors or passageways or anything like that. It's just hard.
Start out by going north, where you will run into the boss door. Nice and close to where you will continue if you die.
If you have the magical key, all you have to do is follow all of the locked doors to get to the boss key, but if not you'll have to do the following.
Go east north and east. From here go south once to get a key, and south again to get the compass. Now go north three times to get another key.
Get back to the room with the boss door by going south west south and west, or by quitting and continueing.
Now go west through the locked door, and then north through the shutters to find another key.
South west and south you can find the map. From there go north four times to get a key.
Head south once, then east, and bomb the east wall to get into the 10-rupee room. From there you can bomb the east and north walls, but you want to exit the room by going north.
Go east twice to find a key, and from there go west and south to find another. Go west to the 10-rupee room and north again, otherwise you will be forced to go all the way around the dungeon to get back where you were.
Next you should go west, and then north through a locked door and east through another. Now go east again to find the final key.
West from there, you'll be at the final locked door. Go north and collect the boss key from the death knights.
Go back to the beginning of the dungeon where the boss door is. From this point on is the last of Ganon's strongest minions in a series of boss battles.
Dark World Palace - Ganon's Hideout - Boss Run:
Well, go through the boss door to fight the first boss. A fire breathing ghoma is nothing to laugh at, but you should be able to beat it pretty easily. Every room from here on has statues of Ganon on the walls that will shoot fireballs at you, so be prepared.
Push the block and fall down the pit and you will have to face three fire gleeoks totalling 12 heads. This may be a bit more of a challenge, but remember that his body hurts you less than the fire, and nayru's love should help if you have it.
North of that is a patra 3. The room is pretty empty so I doubt it will give you too much trouble.
Go north again and you'll come across another fire breathing ghoma, but there are statues everywhere which will make getting an arrow off into its eye will be a bit trickier (but at least the fireballs hurt less than the fire).
Fall down the pit and Ganon will pop up to mock you a little. You will have to defeat group after group of enemies to make it past this room. First is a bunch of blue lynels and goriyas. Then comes a group of splitting darknuts led by two death knights. After that is a group full of bat wizrobes with a few mirror wizrobes. Finally there is a group of stalfos 3 with some rope 2 mixed in, a good time to refill health.
North one room, and Ganon will mock you some more before sending a giant skull to kill you. You'll need to defeat two groups of enemies to make it open an eye. Shoot the eye with an arrow, and then repeat the process with the second eye. Defeat two more groups of enemies and it will open up a third eye in its forhead for you to shoot with an arrow. Kill one last group and it will open its mouth. Bomb the mouth three times and you will destroy the skull.
Ganon will again mock you when you go north, and you will see a turtle head staring down at you. Statues will appear along with moving traps and triggers, all you have to do is push the statues into place and defeat the enemies when the statues come to life. After six times, the turtle will open an eye. Blast the eye with some magic to stun it. The other eye will open, and you should shoot magic at it too. The first eye will open again, but this time shoot an arrow at it, and do the same with the second eye. Finally, with both eyes bright red, break apart the statue with the hammer, then bombs, then hammer again, and finally bombs.
Finally, drop down the pit and Ganon will be there waiting for you. There are statues blocking your path, and not only will Ganon be invisible, but you will be as well. Defeat Ganon against all odds, and you will finally pick up the third triforce and rescue Zelda. Really.