Welcome to Magma Rock, the final elemental rock. This is quite long, and in terms of puzzles significantly more difficult than anything the other rocks have thrown at you. But it's still not as bad as Air's Rock.
Climbing Magma Rock
Go up to the boulder and Lift it up. Ignore the door ahead, and climb around it, up onto the start of the mountain. To save time assign Burst to a Psynergy Shortcut (keep Move as the other). Go to the right-most wall, climb it, and use Burst on the statue. It'll launch a fireball at the cracked pillar across to the left, blowing it apart and allowing you to climb up the next wall across. Go around to the left and slide down the groove. Go around to the front of the statue and use Burst on it. You'll have to do this a fair few times - waiting ages for the statue's lid to explode, lifting it up as a platform on a geyser of lava. Anyway, climb up and jump on, and wait for it to lift you up. Hop across, and climb around to the next pillar. Shove it onto the metal plate and climb up to the next area.
Go all the way to the right and climb down the wall to the previous area, and grab the Oil Drop if you want to. Climb back up and take the right-most ladder up to the two plants. Use Burst on the statue to the left, then reconfigure your Djinn. Once you've got Growth on a character, use it on the right-most plant and climb up the vine. Slide down the groove at the top. Use Burst on the statue to blow up another pillar, then slide down again.
Back at the bottom, use Growth on the left plant and climb up. Use Burst on the statue then climb up and let yourself get carried up to the ledge. Shove the pillar along to the metal plate then go left to the next area. Use the second groove from the right to drop down and get 383 coins from the chest. Go back up using the Burst statue, then back at the top use the third groove from the right. Use Lash on the rope, and use Burst on the statue. You actually have to run for this one; once it's glowing, go down the left groove and hop across, climb up the wall and hop on. Hop to the left when you're blasted up and go up the climbable wall.
At the top, shove the pillar onto the plate and climb around it. Go up the right-most wall to the next area. Go left, hopping over the small trench and around the rocks. Up the ladder, Move the pillar to the right, then go back across the trench and climb the ladder. Use the pillars to hop across, and you can now jump back using the end pillar to break the left-hand cracked pillar and drop down. Go down and use Burst to launch a fireball across and blow up the pillar, then go across the tightrope and slide down the groove. Go back to the right, across the trench, then climb down and around. Shove the pillar across to the plate and go to the right.
Here, go up the ladder, then down the right one and keep climbing down to the previous area. Shove the pillar across onto the metal plate, then go left an area again, and pick up a new kind of forgeable material, the Salamander Tail, from the chest. Now, go back to the right and back up to the top area. Go up the walls to the large climbable wall. There's a similar trial in all of the rocks, isn't there? This time you have to dodge the statues continuously blowing fireballs at you. Thankfully if one catches you it'll break the chain and permanently disable them. Unfortunately there's three pairs to evade. Once you're in the next area, go right and down the groove. Keep going down to the bottom, and shove the pillar across to open a shortcut. Now, use the Burst statues to go all the way back up to the top.
Back up here, go right to the wall, and climb up. Ignore the ladder down here for a moment and go right to another wall you can descend to reach a statue. Use Burst on it, and it'll launch a fireball at the orange-yellow stone in front of the crack in the side of the mountain. It'll dislodge some rocks as well as opening a door into Magma Rock. Next, climb back around and take the ladder you didn't use before to get to the entrance.
Magma Rock Interior
This is where it starts to get hard. The interior of Magma Rock can be very confusing and tricky at times. You can follow the path all the way around to a room you passed through before. Here, going down or left across the pillars lead nowhere, so hop across to the Burst statue, and use it to activate the large head, which spews a torrent of lava into the room. Before you go up, if you didn't get all the djinn from the first game, go to the bottom of the room around the floodgate to get a random missed Mars Djinni, who joins you without a fight. Now go up to the previous room. (the extra-tall doors serve as a means of the lava filling the channels and lower sections of other rooms on each floor) to the previous room. The white tiles on the turquoise paths carved out on the floor begin to serve as moving platforms for you to use once their base is filled with lava. Use the one in this room to get across to the left, and go around to the door. Go left, down, and then to the right and re-enter the lava room on the other side. Go straight down through the next door and grab the Lucky Medal from the chest. Now, go back up and down the left-hand side of the lava room to the floodgate at the bottom. Step on the button to drain the room of lava. Go back up to near the big face, then climb down and push the pillar up to its hole. You don't need to worry about going across these and refilling the room with lava - instead, go through the bottom of the tall door into the previous room - you can now reach the stairs down underneath the big blue stone.
On the next floor, ignore the path right and the Burst statue; go down the ladder to the bottom. Down here, take the tall-door exit below you, underneath the tightrope. In the next room, take the top tall door to the left, and shove the pillar into its hole. Go back, then down through the bottom door. Follow the platform track all the way to the left and climb up. Save, standby Djinn, then obliterate Fury in battle to have it join you. Now, return to the lava room, climb up, and use Burst on the statue to activate the face and fill the room with lava. Navigate the edge of the room (don't leave it - walk across the top of the floodgate, but be sure not to accidentally step on the button and drain the lava away) and go across the tightrope to the bottom left door. The moving platform in here allows you to reach a Mist Potion in the chest. Once you've got it, go back to the left and go down, hopping across the pillar you moved before.
You'll have to be quick in the next room - the platform is only one-way - it won't go back. So you've got to run around the rocks to the right so when it comes past at the edge of the lava you can hop onto it before it goes out of reach. If you miss it, go back to the previous room, and re-enter to try again. Once you're on the right-hand side, go right and through the door. Use Burst on the right-hand cracked pillar. Go up, and use Burst on the left-hand one too (the moving platform leads to a statue which you can use to blow the pillar apart as well, but this takes time, and there's no need to conserve 2 PP over something like this). Hop across the right-hand moving platform and head back up to the lava room.
Use the button to drain the floor of lava, then climb down and leave the room to the bottom via the tall door underneath the tightrope. Go up the now unblocked ladder, and down the next one to the right, to reach the next set of stairs down.
Go down the ladder, and around through the room at the bottom to get past. Go up to the door. You're now in this floor's lava room, and it's considerably larger than any of the others. The door leads nowhere, so head left and use Burst on the statue. Once the floor is filled with lava, use the rings of moving platforms to go all the way across this room to the left-hand side. Exit the room to the bottom. Follow the path down, and ignore the chains for the mean time. Go down into the next room, and use the floodgate in here to drain the floor of lava. Go back to the chains in the previous room and use Whirlwind like you did with the vines in Gaia Rock, or the chains in Jupiter Lighthouse to swing across. Once you reach the ladder, go down, and then go left and up through the tall door.
Up the ladder to the right, above the platform track, is a chest containing another Salamander Tail. Go back left, and up again to the bottom of the lava room. Don't readjust the pillars yet - go up and right to the tall door. In this other floodgate room, you will find a chest containing yet another new type of forgeable material, a Golem Core. Back in the lava room, Move the three pillars into their respective holes, and go through the tall door at the bottom right. Move the pillar across into its hole, and climb up the wall, and through the door to the upper level of the lava room. Fill the floor with lava again, and use the moving platforms to reach the realigned pillars, and go down. In the next room, go right and down to the next room, then down again. Use the moving pillars in here to get to the next door, then head up and move the pillar off.
That was a lot of work to move the first pillar you spotted on this floor. Never mind, use it to jump across and re-enter the lava room by following the path to the north, through the left door. Head up through the door at the top of the room to the floodgate, and use it to drain the floor. Return to the pillar you moved a few seconds before, and hop across and use the ladder to climb down to the stairs.
Go left and shove the pillar off. Go down and hop across to the right and confront the Mimic for an Apple (this is the room you would have appeared in if you had taken the entrance at the beginning of Magma Rock). Hop back to the left and go up through the door. In the next room, when you approach the ring of platforms on the lava, there'll be a rumble, and a load of rocks and fire will land on the edges of the platforms, including one red-hot glowing one (make a note of this later). Navigate the new obstacles to the top door, and follow the path to the "heart" of Magma Rock.
Go straight up (the platforms will disappear as you hop across the endless reef of lava) until you reach the tablet.
"Wielder of Flame's strength, Lay your hands upon this stone. If th'art worthy, I will grant thee the power to Blaze with fire."
Once you've got the Psynergy Blaze for Jenna, use the left-hand path of platforms to reach the random unmovable pillar. What do you do here? Blaze will allow you to shoot flames a short distance, allowing existing fire to spread to other things - for example, torches or ignitable gas. Stand to the left of the fire here and use Blaze to light the other torch, dropping the pillar. Use the next path of platforms to return to the entrance to the "heart" and go back out to Magma Rock's interior. Do NOT use Retreat now - there's something else to get.
Return to the room with the various flames and rocks, and go to the bottom left flame. Stand to the right of it and use Blaze to light the right-hand torch. Hop across and use Blaze again from this side to ignite the other torch, lowering the pillar and revealing a door. Go around back to the unreachable section of this room, and inspect the glowing red rock. Select when it asks you if you want to retrieve whatever is in the rock, and you will get the Magma Ball. Now, you can Retreat your way from Magma Rock, and leave to the world map.
Congratulations, you've just done the last elemental rock, and the second-last non-optional dungeon of the game. The only thing left now is Mars Lighthouse, at the very north of the world. But, you still can't get there. If you attempted to go through the Northern Reaches before now, you would have soon met a huge wall of ice that you can't get past. You need two things to break it down - one of which you just retrieved - the Magma Ball. You can get something to fire this projectile into said wall of ice in the town of Loho, which is accessible via a beach on the western coast of Angara.
So, go back to wherever you parked the boat and return to the Western Sea. Go up to this beach (it's the small one, you can see the town from it), and disembark. Enter Loho.