After rescuing Astrid from the locked room, she opens the door to the Temple of Fire.
Temple of Fire 1F
Go north, and avoid the spinning fire bar. Follow the fire bar around until you can go to the room on the right. Kill the chuchu, then go up to the top of the room and run to the right. Link will automatically jump to the ledge with the locked door. Run to the right again to jump to the right side.
Check on the sign on the right. The sign is telling you about trap doors in the northeast corner of this floor. Open your map and draw the line in the northeast area so you know the safe path to walk.
Then go south, and you will be trapped in a room with Keese. Kill the Keese and then open the treasure chest to get a key.
Go north and run to the ledge with the locked door. Unlock the door, then follow the safe path that you saw on the sign in the previous room. You will find a chest along the way that contains a red rupee.
At the end of the path, you find four crystal switches. Stand in the middle, then draw a big circle around Link to make him do a spin attack.
Go back to the area with the spinning fire bar, and follow the bar around until you can go up the stairs in the north wall.
Temple of Fire 2F
Go to the right, then go north, then west across the blue tiles in the floor. Hit the red switch to change which blocks are raised. Go south, then east, and you can take the east path to be able to go south to the next area.
You will be trapped in a room with green Gels. Hit the big ones and they will split into two. If the small ones get stuck on you, rub the stylus to make them fall off. After you kill all the Gels, a chest will appear. Open it to get the Boomerang.
Go to the right side of the room. Tap the boomerang icon, then draw a line on the touch screen. The boomerang will fly along the path that you drew. Make the boomerang hit the crystal switch on the right. The flames on the left will disappear, so go west.
You will find a room with two torches that spit fireballs at you. Go to the left edge and use the boomerang to hit the two crystal switches. Make sure that the boomerang hits both switches before the boomerang comes back to you. If you do it correctly, the flames on the right will disappear, and you can go down the stars.
Temple of Fire 1F, part 2
There is a stone statue in this room that will tell you if you have found all the treasure chests on this floor.
Go west from the statue and you will find a crystal switch. However, if you hit that switch with your sword, you will be trapped. So stand on the right side of the red tiles, then use the boomerang to hit the crystal switch.
Then you can go south. When you are in the area with flames on the right, use the boomerang to hit the crystal switch on the left side of the area. That creates a shortcut to the exit of the temple.
Go south from there and you will be trapped in a room with two Bubbles. You have to hit the Bubbles with the boomerang to make their flames go away, then hit the bouncing skulls to kill them. The Bubbles always go in a straight diagonal line.
After you kill the Bubbles, you can go up the stairs in the southwest corner of the room.
Temple of Fire 2F, part 2
In this room, there are Fire Keese that can only be killed with the boomerang. If you want all the treasure on this floor, be sure to kill all of the Fire Keese. There is a statue in the southwest corner of the room that will tell you if there are any treasure chests on this floor. Go east from that statue to find a lever in the wall. Pull it.
Now go to the north side of this room and run east to jump to the platform with the large spinning fire bar. Run east again to jump to the right side. Kill the Fire Keese here to make a treasure chest appear (if you also killed the Fire Keese on the west side of the room). It contains a red rupee.
Now go south and pull the lever on the left. This will open the door in the west middle part of this floor. Go there, and stand just outside of the door to make the mouse run back and forth between the holes in the wall. Use your boomerang to hit the mouse and get the key.
Then go to the southeast part of this floor and you find that your path is blocked by red blocks. Use your boomerang to hit the crystal switch down below. Then go up to the area between the red tiles and blue blocks, and use the boomerang to hit the crystal switch again. Then go east and unlock the door and go up the stairs.
Temple of Fire 3F
Go south from where you entered. Go past the spinning fire bar, then go to the left and check on the sign. Mark your map with the numbers that you see.
Then go north and kill the green Gels. Then go north and you find two candles. Have Link look at each one, and blow into the microphone to blow each candle out. Then go north.
Stand on the tile in the middle and use the boomerang to hit the four switches in the order that you saw on the drawing. A key will appear. Use the boomerang to get the key. Then go southwest and unlock the door.
To the right, there is a statue that will tell you if there are treasure chests on this floor. Go west from there and you will notice a strange locked barrier.
Go west and you will be trapped in a room with fire keese, electric chuchus, and a torch that spits fireballs at you. You have to use the boomerang to kill the fire keese. You can hit the electric chuchus with the boomerang to stun them, allowing you to hit them with your sword without getting zapped with electricity. After you kill all the enemies, you can go north.
Hit the Bubbles with the boomerang to get rid of their flames, then hit them with the sword to kill them. This makes the flames up north go away. Go north and read the sign. You need to light all three torches. Go north and step on the switch to make one torch light up. Then make the boomerang go on a path through the flame and on the two unlit torches. The boomerang will carry the flame to the other two torches and light them up.
The flames in the northeast area will disappear. Go southeast to where you can see a spinning fire bar on the right. Use your boomerang to hit the crystal switch that is northwest of the spinning fire. This will make a path appear on the right. Go north to find a treasure chest that contains the Boss Key.
You need to carry the key to the barrier in the middle of the south side of this floor. Go south and follow the fire bar around, then make your way to the middle of the southern area. Tap the locked barrier to put the key in. Then you can go north up the stairs.
Temple of Fire 4F
Check on the upper-left sign to make a blue warp point appear. You can step on it to go back to the entrance. There will be another blue warp point at the entrance that will take you back to this room.
When you are ready, go north up the stairs.
Blaaz, Master of Fire
Go north and the door will lock behind you. Blaaz will appear and split into three. Look at the map in the upper screen and you will see that each skull has spikes on top. One skull has one spike, one has two spikes, and one has three spikes. You need to use your boomerang to hit the three monsters in the correct order (the one-spike skull, then the two-spike skull, then the three-spike skull). When you do this, the three monsters will combine into one, and you can hit Blaaz with your sword. Hit him repeatedly, and watch the upper screen to see where he goes when he disappears. Blaaz might push you down while you are hitting him, but this doesn't reduce your hearts. Be careful to avoid any shadows that appear on the ground so you won't get hit by the eruptions. Eventually Blaaz will split into three again, so repeat the process until Blaaz dies.
Meet the Spirit of Power
After you defeat Blaaz, there will be a cut scene. Leaf will join you.
Open the treasure chest to get a Heart Container. Then go north and step into the blue light to be warped out of the temple.
Outside, you can go up to the mountaintop and go to the west of the volcano crater to find a chest. It contains a red rupee.
Then you can jump down the ledges to reach Astrid's house. She tells you that in addition to the Spirit of Power, you also need to free the Spirit of Wisdom and the Spirit of Courage.
She tells you to go back to the Temple of the Ocean King on Mercay Island. She also gives you a Power Gem.
When you are ready to leave, go back to the dock and talk to Linebeck. Then draw a path from your ship to Mercay Island. If you see a golden frog jumping out of the water, just ignore it for now.
The Phantom Hourglass
Back on Mercay Island, go north from the dock, then west, and go back into the Temple of the Ocean King. In a cut scene, Oshus tells you to go up to the altar, so go to the left or right of the room to go up the stairs, then go to the back of the room. You will get the Phantom Hourglass.
Oshus explains how it works. The hourglass prevents the temple from draining your life, but when the sand runs out, it can't protect you anymore. You can recharge the hourglass by going outside. Oshus says you can add more sand by defeating more monsters hiding in temples around the world.
For now, you need to go into the temple to find the clue to freeing the next spirit.