This part will take you through your third visit to the Temple of the Ocean King.
Return to Mercay Island
Now that we have our second spirit fairy freed, it's time to head back to the Temple of the Ocean King for our next clue. Return to the dock at the Isle of Gust and have Linebeck get the ship going again. Plot a course directly south to the Southwestern Sea (you don't need to go through the foggy part again) and then to Mercay Island, using the cannon to blast away any monsters and Sea Traps that happen to be in our path.
Once we're at Mercay Island Harbor, head back up through the same path as before to the Temple of the Ocean King. Now we can bomb the blocks that stood in our way, and that cracked wall reveals a cave entrance into which we can get ourselves a Power Gem (if we're collecting those things throughout the game).
Inside the Temple
We now have 12 minutes in the hourglass and three more floors we need to pass through to get what we need this time. We'll be going through the same three floors as before, but at least two of them will not be as difficult now.
Just go straight up through the two Safe Zones to the door in the center of the floor.
Now that we have Bombs, we can get the small key much faster than before. From where we entered this floor, move right and then up and then to the left where we see blocks we can blow up. Use a Bomb to blow them up, then move left to press the floor button, opening up the same door as before to get the small key. Then just bring it to the locked door and open it. Simple as that.
Use the same initial strategy as you did the last time you were here: go south and hit the switch orb on the left, then go up and pull the switch and then go to the left and hit that switch orb to make the key drop down into the room in the center. This time, though, go back to near the first switch orb that we hit: you'll see a crack in the wall that's south of us. Throw a Bomb at that part and go through the opening it makes. Stand on the floor button located at center east and use the Boomerang to snag the small key located in the center room. Then just go through the crack again and bring it to the locked door and open it.
The same strategy you used the last time you were here still applies. However, you can now use the Shovel to get to the plateau in the southeastern section faster by riding the air up to it.
The hourglass stops flowing again, so we get a bit of reprieve. This time we see a door that has the seal of the Spirit of Wisdom on it. Neri will give us the power to open this door so we can move on.
On this floor full of gust-blowers, we have a new enemy to deal with: Phantom Eyes. These evil peepers love nothing better than to spot us and alert the Phantoms to close in on you. They also stick close by you, and if you get two of these things on you, they'll slow you up, requiring you to do a quick rub to break free. Fortunately, Phantom Eyes can be slain. The best strategy to deal with them is to hit them with the Boomerang when you're not in their line-of-sight, then strike them with the sword.
From our starting position, go to the right, and then down until you reach the first gust-blower that blocks your path. Around one corner is a Phantom Eye; around the other corner is a switch orb. First hit the switch orb with your Boomerang to shut off the gust-blower, then hit the Phantom Eye with the Boomerang to stun it before you slay it.
Now go down, then left, then down, then left, then up while watching the nearby Phantom's movements. There's a small key in the room immediately north to us, but we can't get to it because there are spikes in the door. Now go to the left, then up, and then left, watching the movement of the Phantom Eye in the northwest section. Try to kill it quickly, but soon another Phantom will emerge in the northeast section. If not, use the red pot to hide out in the white spot until the Phantoms and Phantom Eyes pass. Make your way to the Safe Zone at center west and then use the Boomerang to stun the eyes from safety before emerging to kill them. Slaying all the Phantom Eyes will make a treasure chest appear in the Safe Zone at center east which contains a Power Gem.
Go east of the Safe Zone at center west, and you'll see a crack in the wall that you can use a Bomb to blow up. Behind the wall, there's a switch orb you can hit to get rid of the spikes blocking your way to the key.
Go to the southwest corner and you'll see a mound of dirt that you can dig up using the Shovel. Ride the air gust to the platform where the switch orb is and hit it. That will shut off all the gust-blowers on this floor. Now go over to where you found the key and, being careful not to be spotted by the Phantoms, head over to the locked door at the south end and open it to go on to the next floor.
Head over to the left, past the spikes, and then go up into a room that will close the door behind you. You will have to fight off four Electric Chuchus to open the door to the right that will take us to our next closed-door battle with some Miniblins. Finishing them off will open a door to the north where our way to the door to the next floor is blocked by a gust-blower. Use the Boomerang to hit the switch orb over to the right to shut it off, and we'll also get a chest that contains Red Potion for restoring six hearts. Proceed to the left and then enter the door.
There are six stone tablets on this floor that we can go over to read that will give you clues about the "sacred crest", but ultimately we want to reach a red door near the south end that's being blocked by gust-blowers and patrolled by a Phantom. Go to a floor button that's near the left or right side of the red door to shut off the gust-blower, then quickly duck into the Safe Zone and touch the door. It will say, "in a single stroke, draw the sacred crest to reveal a new path". Simply draw the shape of the crest with one pen stroke (if you haven't figured this out, it's an hourglass), and the same symbol will form on the door and then open, allowing you to go on to the next floor.
Sacred Crest Chamber
The hourglass has stopped again, but instead of a chamber with a treasure chest containing a Sea Chart, we have one with a large sun-shaped symbol at the top of the steps. It will show us an imprint that has the sacred crest on it, and we need to imprint this on our map. Get out your Sea Map, select the Southwestern Sea, and then close up your Nintendo DS for a second or two before opening it up. The sacred crest now appears on your map!
Now it's time to show this to Linebeck. Step into the blue portal that appears to leave the Temple.