After you climb Eldin Volcano and find the missing key, you enter the Earth Temple.
Get the Bomb Bag
Go across the rocks floating in the lava, then turn right. As you approach the soft soil, Red Chuchus come out. Kill them, then dig in the soil to reveal an air geyser. Float up the air to get 20 rupees.
Go down from the ledge, and go west, jumping across two rocks in the lava. You find Fire Keese in the archway ahead. After you get past them, you can talk to the Mogma up ahead. It's Cobal. His partner Ledd is missing. Near Cobal, don't dig the soil on the left because a Red Chuchu is hiding there.
Go back across the two rocks in the lava, and go up the stairs. Wait for the two rising platforms to both be at the same level, then go across them to reach the paved platform ahead.
There are two gear ropes on each side. Cut them with your sword. There is another gear rope on the right side of the door. Launch your Beetle at it to cut it. Go through the door.
You will encounter your first Lizalfos up ahead. Fi will tell you to target it and press down to call her and get her advice. She will say that its arm guard will block your sword, so you have to pay attention to which angle is required to hit the Lizalfos. The Lizalfos might also rotate and then do a spinning tail attack, so be prepared to Shield Bash or do a backflip to dodge (to backflip, press the Action button while moving backward and holding the Lock On button—press the Help button if you don't know which buttons these are).
There is a fallen statue in the lava up ahead. There are Bomb Flowers on the statue, so launch your Beetle and hit a bomb with it to set it off, making the other Bomb Flowers explode. A large stone eyeball will roll over to you. Jump onto the ball and you can roll around on it in the lava. If you start to fall off, just stop moving. You will automatically center yourself on the top of the rolling rock whenever you stop.
Roll over to the area to the southwest where a platform is rising and falling on the lava. Throw a bomb onto the platform when it goes down, then it will explode on the rocks, allowing you to reach a chest that contains a golden skull.
Now jump back onto the eyeball in the lava and roll to the area in the southeast side of the room. You can use your Slingshot to stun the Magma Spume along the way, and you can roll the eyeball over it to kill it. In the southeast area, you will find Cobal's partner Ledd, who asks you to get his bomb bag back. It's on the other side of the rock barrier in the wall. Crawl into the hole in the cage on the left and kill the Bokoblin in here. Climb up the ladder. There is a chance of finding an Amber Relic at the top. Walk along the top of the metal fence to reach soft soil. One of the soft soil spots contains a fairy. If you catch it in a bottle, you might want to unequip and re-equip your shield so that the Pouch button will be set to your shield instead of the bottled fairy. That way, you are less likely to accidentally use the fairy when you don't mean to.
Go back down to the lower area, and roll a bomb through the small hole in the fence to the south to break the rocks.
Go through the door that you revealed beyond the rocks. Two Lizalfos will attack you. Try to get the Lizalfos away from each other so you only have to fight one at a time. Remember to swing the sword in the direction that isn't blocked by the arm guard. Be ready to do a Shield Bash in case they are preparing to attack. When each one dies, it might leave behind a lizard tail, so be sure to collect those. When they are gone, open the chest that appears. It contains the bomb bag.
Before you leave the room, check next to the door in case there is an Amber Relic there. Then leave the room and Ledd will talk to you. Tell Ledd that his friend is worried. Ledd will give you his bomb bag. After you try to go farther, Ledd will give you five bombs. You can also put Bomb Flowers into your bag. Just pick up the Bomb Flower and press B. You can crawl into the cage that you went into earlier and fill up your bag with the Bomb Flowers in there.
Get the Map
Jump back onto the eyeball in the lava and roll over to the center platform, where there is a Bird Statue. Walk to the west side of the room where a cracked stone is blocking you on the ledge. Throw a bomb on top of the cracked stone to get rid of it. Jump across and kill the Lizalfos, then go through the door.
Jump over and kill the Bokoblin. You can kill the flame-spitting Magma Spumes in the lava by throwing a bomb at them. Go to the west side of the room and jump onto the rising platform when it falls. Kill the three Bokoblins and open the chest above to get the dungeon map. There is a spot of soft soil behind the chest.
Get the Dragon Sculpture
Now go to the exit of this room and take the Amber Relic next to the door (if any) and dig in the soft soil. Then leave the room and you will be back in the room with the rolling eyeball in the lava. Jump back onto the eyeball and roll under the bridge on the west side of the room. Stop at the ledge with the chest on it. Open the chest to get a Blue Bird Feather. There may also be an Amber Relic on this ledge.
Then get back onto the rolling eyeball and go to the north bridge. There is a round object sticking out of the side of the bridge. Roll into this object to push it in. Part of the bridge will rise.
Now roll to the east side of the room, and go just north of the cage. Look at the wall to see a small crack in the wall. Throw two bombs at it to break open a hole in the wall.
Roll through the new passage. After the first lava spout, roll to the ledge, then hop off of the eyeball. Kill the nearby Magma Spume by throwing a bomb at it, then go into the cave at the end, to refill your bombs. There may also be an Amber Relic near the bombs.
Then jump back onto the eyeball and roll past the second lava spout. You will reach a barrier with a Bokoblin standing on it. To get past it, look to the left to see a crack in the wall. Throw two bombs at the crack in the wall to open a path. (See the previous paragraph on how to get more bombs if you need them.) Then go through the hole that you made in the wall, and when you reach a point where there is a lava spout in front of you, go left. You will reach a big red gate. Use your Beetle to cut the gear rope on top. Then launch your Beetle again and send it through the passage beyond the Bird Statue to reach the other side of the red gate, where there is another gear rope. Cut it to open the gate.
Roll through where the gate was, and you can jump off onto the metal platform there, and go to the end of the passageway to reach the Bird Statue that your beetle flew past a moment ago.
Get back onto the rolling eyeball and wait for the lava spout to the north to stop pouring, then go past. Carefully roll across the narrow lava bridge and kill the Fire Keese at the other side.
Kill the Lizalfos on the ledge and open the nearby chest to get 20 rupees.
Then roll to the nearby bridge. Roll into the round object sticking out of the side of the bridge to push it in. This will raise the bridge the rest of the way. If the bridge isn't high enough for you to go through the north door, you will have to go all the way back to the west side of the bridge and roll into the round object on that side of the bridge, to raise the bridge the rest of the way.
Once the bridge has been raised all the way, you can optionally roll to the southwest side of the room and put more bombs into your bomb bag there (roll under the north bridge to get there). Then roll to the platform in the center that has the Bird Statue on it, cross the north bridge, and go through the north door.
Jump across and run up the slope. As you run, some boulders will roll down from the ceiling. Look for the gap in the rocks on the left side and run through it. Then run up onto the gap in the wall on the left (make sure to keep running until you are on flat ground) to wait for your stamina to refill. Then run to the top of the slope.
Let your stamina refill, then jump over the narrow gap, and crawl through the hole in the fence on the other side. Dig open the air geyser on the right and float up to the stairs that go up the side of the room. There is a ledge at the top and you can see some rocks in the wall across the way. Look to the right and you will see a scratch on the tiles of the slope. Throw a bomb at that scratch or just above it. If timed correctly, the bomb will explode on the rocks in the left wall.
After you break the rocks, go back down the stairs and run up the slope to the gap that you just opened in the left side. After your stamina refills, run up to the top of the slope.
In the next area, you will notice the boss door behind the huge lava spout. Save at the Bird Statue. Go up the winding narrow stairs and walk up the slope (no need to run.) At the top, you will find the Dragon Sculpture.
Open the Boss Door
When you go back the way you came, a giant boulder will come out of the dragon's mouth. Press the Lock On button if you want the camera behind you, then run down the slope, and run onto the stairs to the side of the slope as soon as you can. If that boulder hits you, you will die and get a game over screen, so be quick.
After the boulder passes by, it will go into the lava spout and stop the lava from flowing.
Go to the boss door and use the dragon sculpture on it. Rotate the sculpture, grabbing and releasing it multiple times if needed, until it lines up with the shape in the door. When you have matched the shape, the lock will start glowing and you can put the sculpture into the lock. Go into the boss door.
Go up the slope and you will see a boulder rolling through some ribs. Replenish hearts and bombs here if needed, then walk farther ahead and Fi will make an observation about the nearby chain.
Go up the slope and there will be a cutscene, and then the boss battle will begin.
Scaldera
This battle takes place on a narrow slope. If you need hearts or bombs during this battle, go up to the top of the slope.
Scaldera will walk up the slope, or if its body flares up, it will run. While it is running, you need to dash up the slope in order to move quickly enough to avoid it. If it flares up but doesn't start running, just wait in front of it to see what it does next.
When Scaldera opens its mouth and takes a deep breath, throw a bomb at it. If the bomb is close enough, Scaldera will inhale it. If it explodes before Scaldera inhales it, Scaldera will roll down to the bottom, so be sure to follow it. If you take too long to throw a bomb, Scaldera will start spitting large fireballs that you will need to sidestep.
When you successfully throw a bomb into its mouth, it will be stunned and you will be able to see its eye. Hit the eye with your sword as many times as you can. Scaldera might move its eye around, so reposition as needed.
When you are close to the top of the slope, stay out of range of the bomb flowers on the side. If Scaldera's body is on fire, the Bomb Flowers will explode, but Scaldera will keep walking upward. But if Scaldera's body is not on fire when it steps on the Bomb Flowers and makes them explode, Scaldera will roll back down to the bottom. Follow Scaldera to the bottom of the slope so you can be close enough to throw another bomb when it opens its mouth.
Eventually, Scaldera will stand higher up while running, leaving a space under it that you can run through. It will move too quickly to outrun at this point, so run under it and wait for it to roll back down, while avoiding getting too close to any Bomb Flowers on the slope that may explode. If you are farther down the slope from Scaldera when it starts rolling downward, go to a side of the slope to avoid getting hit. Follow it down, wait for it to open its mouth again, throw a bomb, and hit its eye until it is defeated.
Get the Amber Tablet
After the battle, get the Heart Container, then go up the slope and refill your bomb bag. Then go to the top of the slope and go through the door with the glowing crest on it.
Inside, you will see a cutscene. After that, use a Skyward Strike on the crest to get the Amber Tablet. After another cutscene, use the Bird Statue outside to the left to save the game.
Return to Skyloft to prepare before you move on. You can get wallet upgrades and other items from Beedle's Airshop, retrieve your Wooden Shield from the Item Check (which is recommended, because many enemies in the next area use electricity, which the Iron Shield is vulnerable to), get more Bomb Bags at the Bazaar, and go to the chamber beneath the Goddess Statue and put the Amber Tablet in place. Don't forget to check your map and open the chests in the sky that you unlocked with Goddess Cubes.
Pumm's Next Request
Once you have the Amber Tablet, you can go back to the Pumpkin Landing and talk to Pumm to find out his next request. He will only have requests for you if you broke the Pumpkin Landing chandelier earlier.
For his second request, he asks you to help Kina move the pumpkins to the storage shed. If it's night time, sleep in a bed until morning, then talk to Kina outside of the Lumpy Pumpkin.
You need to carry a stack of five pumpkins to the storage shed area that Kina shows you. Walk very slowly to ensure that the pumpkins don't fall, and if they start leaning, move in the direction that they are leaning toward. As soon as you have gone far enough into the storage shed area, Kina will say that you're done.
You don't get a reward for this task, but you will need to do it if you want to complete all the tasks for Pumm. He doesn't have a new task for you yet, so you will have to come back later.
Piece of Heart
Now that you have the Bomb Bag, you can return to Faron Woods to get a Piece of Heart. There is a rock wall north of the "In the Woods" Bird Statue that you can bomb to find the Piece of Heart.
Continue On
When you are ready, fly into the yellow column of light to reach Lanayru Desert.