This part will take you through your second visit to the Temple of the Ocean King.
Return to Mercay Island
Once Link is outside the Temple of Fire, Ciela will notice that the volcano has stopped erupting, taking it as a good sign. Go back down to the bottom of the island and head for the house in the village where we found Astrid. Linebeck is also waiting for us there, and Astrid will tell us we will need the spirits of Power, Courage, and Wisdom to find the Ghost Ship. Though she cannot tell us where the other two spirits may be found, she does say that our next clue can be found in the Temple of the Ocean King. So we need to return to Mercay Island to find that clue. She will also give us a Spirit Gem (in particular, a Power Gem), which will come in handy when we collect enough of them along our journey. Though we won't cover in great detail where these Spirit Gems are (which also include the Wisdom Gem and the Courage Gem), collecting enough of them will enable Link to have certain power upgrades.
Now that we got what we have done on the Isle of Ember completed, let's get back on the ship and plot a course to Mercay Island. Again, there will be nothing that will be a challenge for us between here and there, so just relax until we get there.
Once we're at Mercay Island Harbor, head back up through the same path as before to the Temple of the Ocean King.
Inside the Temple
Once we enter the first room at the entrance of the Temple, Linebeck will appear, warning us to be careful because it can "suck the life out of you". Oshus will also appear and direct us to the altar at the top of the stairs where the hourglass is. Go up the stairs and grab the hourglass. You'll notice that sand will flow into the hourglass. Oshus will tell us that this is the Phantom Hourglass that will give Link a limited amount of protection from the Temple's curse as long as the Golden Sands remain in the hourglass, and that the only way it can be recharged is if we return to the sunlight. This will be very necessary for exploring the other floors of the Temple to retrieve other Sea Charts, but it will also put pressure on us to reach those Sea Charts within a limited time. Fortunately, the hourglass will stop as long as we're in the Safe Zones.
For now, though, we will have ten minutes to reach the floor where the next Sea Chart is. Counting Floor 1, this will be four floors, and three of them will be challenging. You can usually complete these floors in under ten minutes with the hourglass running. If not, just continue to practice running through the floors until you get the timing and movements down.
Just go straight up through the two Safe Zones to the door in the center of the floor that has the seal of the Spirit of Power on it. Leaf will be able to open this door so we can venture into Basement 1.
As we enter this floor, two knights in armor will instantly appear. These are Phantom Guardians that are inhabited by evil spirits that protect the floors of the Temple. Phantoms cannot be harmed by any of our weapons at present, but they can hurt us with one strike, causing us to lose time and to start what we have to do on that floor all over again. Our best defense against them is to avoid them by watching their movements and by using the Safe Zones to duck into so they can't see or touch us. On this floor one Phantom will move in a clockwise circle around the southeastern section, while another Phantom will simply move north and south along the west side.
From where we entered this floor, move right and then up to the northeastern corner where we see a switch orb, then hit it and move quickly to the Safe Zone located in the south middle, avoiding the Phantom. The switch orb causes a torch to light up near the Safe Zone, but it will go out within a limited time. From the Safe Zone, quickly direct the Boomerang to hit the lit torch and then hit the unlit torch across from it to light it. (If the torch goes out, you'll have to hit the switch orb again to relight it.) This will cause a wall of fire near the southwestern corner to go out. Now move toward the left and watch the Phantom's movements as you go north toward the northwestern corner, using the Safe Zones to duck into, then go to the right and press the floor button, causing a door in that corner to open. This will give us a small key that we need to take to the locked door in the northeastern corner and open it to reach the next floor. On your way back there, grab a red pot and smash it while you're following the Phantom going north and south along the west side: it will act as a Safe Zone when you stand on the white spot it creates, causing Link to be invisible and intangible to Phantoms; they will pass by and through you as if you weren't even there.
Two Phantoms will appear on this floor: one of them will stand next to a switch and will just look from side to side until it hears a noise, and the other will move around in an L pattern along the south side. Just go down until you see a switch orb on your left and hit it, causing the nearby Phantom to move south to investigate. While he's distracted, go up to the switch and pull it, then quickly hit the switch orb to the left of that switch. The switch you pulled will cause a wall of fire blocking access to the south part of the floor to go out, and the switch orb will cause a small key to drop into the room near the center. Quickly head to center west where a red pot is, and if need be, smash it to avoid a Phantom if he sees and chases after you. Immediately south of center west is a wall of fire that needs to be put out. Use the Boomerang to hit the switch orb on the other side to put it out. Now go down into the Safe Zone in the southwestern corner and watch the movement of the Phantom along the south end. If you still have a red pot that you haven't broken yet, carry it and use it to hide out from the Phantom until he goes toward the west, away from center east. Stand on the floor button located at center east and use the Boomerang to snag the small key located in the center room. Now head over to the room just south of where you got the key and hit the switch orb to cause the blue blocks to go up and the red blocks to go down, allowing you to reach the locked door a little west of center and open it to reach the next floor.
Two Phantoms will move in circles on this floor: one in the northwest section will move counterclockwise and the other in the southeast section will move clockwise, and that one has a small key that we need. For now, though, head east and then north into a purple-tiled room where we see three triangular pedestals in the shape of the Triforce. We need to gather three things on this floor to put on those pedestals and cause the nearby door to open to the next floor, where our clue to the Ghost Ship awaits.
From that room, head right and then down, but stop before you reach the ledge. There's a switch orb we need to hit nearby, so get out the Boomerang and hit it to disarm the spikes that are also nearby. Now drop down and head to the Safe Zone in the southeast corner where a chest awaits, keeping out of the Phantom's sight. In the chest there is a Force Gem, which is what we need to put on the pedestals. Force Gems will slow us down when we carry them, so we need to watch the Phantom's movements carefully and drop them if we've been spotted. (Also, if we're near the south of the room where the pedestals are and we're spotted, a wall of fire will burst forth and will only go out when we're out of danger.) With this Force Gem from that location, just go to the left and then up into the room and simply toss it in when we get there.
The second Force Gem is located in a Safe Zone in the northwest corner. Go there, open the chest to get it, then safely lug it around to the room where the pedestals are.
The third Force Gem is located in a Safe Zone behind a locked door in the southwest section. To get that, though, we need to snag the key from the Phantom who has it. First, pull the switch that's located in the southwest corner to make a wall of fire at the southeast section to go out. Then, while avoiding a run-in with that section's Phantom, go up the stairs to a plateau where we can go around to the floor button on the lower left and press it when the Phantom is immediately to our left, which causes a trap door to open for the Phantom to fall into so we can grab the key. Now take the key to unlock the door, open the chest that has the Force Gem, and lug it safely up to the room with the pedestals.
Now the door will open and we can move onward.
As soon as we reach this floor, Ciela notices that there's no fog in this room and that hourglass has stopped ticking down. All we have to do now is go to the left and up into the Safe Zone room to open up the treasure chest. This will contain the Sea Chart that will open up access to the Northwestern Sea. In the room to the right of us, a blue portal will open. Go there and step into that portal to leave the Temple.