The Legend of Zelda: Phantom Hourglass/Return to Mercay Island
 Back to Mercay Island
Set a course for Mercay Island and head back to the Temple of the Ocean King.
 Temple of the Ocean King
Do as Oshus says and get up to the altar. You will obtain the Phantom Hourglass, which shields you from the life-draining effects of the cursed temple for a limited time. You start off with 10 minutes of protection. This only drains while you're in the beige areas of the map, so the time does not go down while you are in a safe zone. Head to the door that the Spirit of Power pointed out and tap it, then go down the stairs.
 Floor B1
As you enter the floor, two Phantoms spawn. These phantoms are guardians of the temple. If you cross into their field of vision (the yellow cone coming out of their icons on the map), an alert will sound and they will chase you. If they catch up to you and hit you, not only are you sent back to the beginning of the floor, but you lose some time from the hourglass. You can escape to any safe zone. Get used to this type of action, as you'll be revisiting the temple multiple times throughout the course of the game.
Head to the north-eastt corner of the floor and hit the switch, lighting a torch for a short time. Hurry to the safe zone below the starting point and next to the torch. Use the boomerang to light the unlit torch by passing the boomerang through the lit torch first. Work your way up the west side of the floor, hiding in the safe zones and letting the phantom pass. At the top, turn right and break one of the red pots. These red pots contain magic which creates a small safe area wherever you break the pot. Hide in it, and look for the switch to the right. Step on it and get the key from behind the door that opens. Now, go all the way to the north-east corner of the room and unlock the door and go down the stairs.
 Floor B2
Head south and hit an orb switch in the alcove. Run west then north to another orb switch and hit that as well. The key will drop behind a set of spikes which you will encounter later. If you've managed to grab the Phantom's attention, that's OK. If you haven't yet, get its attention. When the Phantom charges towards you, it will abandon the lever switch it was guarding. Quickly run away from the Phantom and take the long way around one of the center pillars to reach the switch. Pull the switch and retreat to the safe area. When the coast is clear, run towards the flame wall that the wall lever deactivated and run all the way west. Break the red pot and stand in the safe zone. Pull out your boomerang and hit the switch just beyond the flames to kill said flames. Run south and stand in the safe area.
When the Phantom turns its back to you and is heading north, run straight to the east and break a red pot to stand in a safety zone. Once the Phantom is heading back west, run north and step on the button to lower the spikes. However, if you leave the button, the spikes will rise again. Therefore, use your boomerang to retrieve the key from behind the spikes. When the coast is clear, run into the area where the blue blocks are and activate the orb to lower the red blocks. Being careful to avoid detection by the Phantom, make your way to the locked door and go down the stairs to B3.
 Floor B3
Once the Phantom patrolling near the door moves away, run to the west, smash the red jar, and run up to the safe zone and the chest containing a Force Gem. You need to bring the Force Gem to one of the three pedestals in the big safe zone. However, Force Gems will weigh you down and make you go slower, so you have to be careful when making your way back. If you've been quick about it, however, you can probably run straight to the pedestals without incident. Tap a pedestal to drop the Force Gem into it.
Once the coast is clear, run to the south-west corner of the floor and pull the lever to kill the flames blocking a set of stairs. Make it to those stairs, go up them, and smash the red jar. There are two switches up here. Both of them will trigger a trap door to open. Pick one of these switches. Trigger it once just to see where the trap door is. Retreat to the safety of the red jar and wait for the patrolling Phantom to walk over where the trap door is. Quickly run to the switch, press it, and hopefully the Phantom drops through the door and leaves behind a key. Try again if you don't get it the first time.
Pick up the key and unlock the door in the south-west corner of the room. The door hides a Force Gem. Bring it back to the pedestals. Run to the south-east corner of the room and pick up the final Force Gem from the chest and bring it back to the pedestals. Enter the door that opens.
This area isn't cursed, so the hourglass won't deplete here. Go to the north-west corner, grab the sea chart, and enter the blue warp to go outside.
 Mercay Island
Exit the temple and head back to Linebeck's ship. A guy on the pier informs you that you can get a cannon from Eddo on an island to the south. Speak to Linebeck and he notices that the chart is very dusty. Blow into the microphone to clear off the dust and reveal another crest on an island in the Northwestern Sea.
 The Southwestern Sea
Set sail for the Northwestern Sea by drawing a route that goes all the way to the top of the chart. But once you get to the northern edge, a storm tosses you back. For now, go to Cannon Island, south of Mercay Island.
 Cannon Island
Head into the building to the east. Speak with Fuzo to learn that Eddo has locked himself in the shop, so you'll have to go the long way around the island to reach him. Head to the gate that Fuzo has opened for you.
Follow the path, defeating a couple of ChuChus that pop up. A sign informs you of riches hidden in the beehives. A short distance down the path is a bee. The best way to defeat the bees is with a spin attack. Head south to an intersection and go east to a clearing. Defeat the bees and open the chest to get a treasure map. Later, once you get another attachment for the ship, you can make use of these maps. For now, just move on. Follow the path until it leads to a cave.
 Bomb Garden
Kill the rats in the first room. Tap on the bomb flower to pick up a bomb, move to a good position, then tap the rocks blocking the way to the next room. The bomb will explode, taking the rocks with it. Go back to the bomb flower, pick up another bomb, and run to the next room. Chuck the bomb at the block that is preventing the push block from moving. Go back and grab another bomb. Run to the easternmost edge of the room and throw it at a crack in the wall. Be fast about it, or else the bomb will explode in your hands. Go through the hole in the wall and pick up a Power Gem.
Back at the push block, push it forward two spaces and pass by it. Pull the next block you encounter down all the way, then pull it west a couple of spaces. Continue on and pull the next block east one and north one. Kill the rats and run back to the bomb flower. Pick up the bomb, then run to the rocks blocking the path and blow them up. Go up the stairs.
Be careful when killing the rats here, you might set off a bomb with your sword. Destroy either set of blocks with a bomb, then head south-west to find a chest with 20 Rupees. Continue along the path to the right and destroy some more bombable blocks. Head down the stairs and continue along the path, killing all the enemies that pop up. When you get to the set of three bombable blocks, run back up the stairs to the northern bomb patch. Grab a bomb, hop off the ledge to the north, and run to the east until you can see the bombable blocks on the other side of the fence. Toss the bomb at them and clear your path to Eddo's workshop.
 Eddo's workshop
Speak with Eddo. Buy the cannon for the jaw-dropping price of 50 Rupees. Head back outside. Notice the bouncing mailbox? That means you have a letter. The postman drops by, reads the letter, and asks you to sign. Make it as pretty or ugly as you wish. Approach Linebeck and get back on the open ocean.
 The Southwestern Sea
Now that you have the cannon, you can attack things. Simply tap on something with the stylus to shoot a cannonball at it. You may see a golden frog leaping out of the water at various points in the ocean. Don't bother with them for the time being, as nothing useful will happen right now. Set a path for the western edge of the sea. Along the way, there will be some dark rocks blocking your path. Blast through them with the cannon.
You will catch a glimpse of the Ghost Ship at this point. Follow it! Eventually, the fog will thicken considerably. Follow the Ghost Ship into the Northwestern sea regardless. Watch out for floating barrels of explosives, which you should destroy with your cannon. Eventually, you will become completely lost in the fog and end up back at the southern edge of the Northwestern sea. Run back to the Southwestern sea. Before you head to Molida Island, the only island left, head to the Adventurer's Ship to the south.
 Guard's Ship
Kill the Miniblins that have beset the poor guard and talk to him three times. After the third time, Nyave introduces himself and gives you a piece of treasure. As it turns out, every day Nyave's ship gets overrun by monsters. Each time you save him, Nyave gives you some treasure. This becomes a great opportunity to make Rupees once the treasure teller opens. By manipulating the DS internal clock, you can very quickly build up a store of treasure that you can unload at the treasure teller for easy money.
Now, exit the adventurer's ship and go to Molida Island.