Go on ahead and enter the tower. If you came here before getting Parch from Aqua Rock you'd be stuck straight away. Use Parch on the right-hand body of water and go down through the door. Head along the path around the bottom of the next room and up the stairs at the top. Go down the bottom door up here and navigate the ice to get a Mint from the chest. Now go back up through the top door.
Don't use the ice here yet; go along the path at the top to get 365 coins from a chest. Now use the ice to slide off the ledge and exit via the bottom door. Back in this room, you can slide to get to the ladder. Climb up and use the door. Go up to the stairs, and in the next room, use the stairs at the bottom of the room. Use the ice here to slide off and down a level. On the floor below, you can navigate the ice to get to the Mars Djinni.
Reflux, the Mars Djinni
When you collide with it, you'll knock it to the floor on the right-hand side. Slide after it and defeat it in battle to have it join you. Slide back to the door on the left, and slide down the groove to return to the bit you were at earlier. You want to take the left-hand stairs this time. Pound the pillar to crush it. At the end of the path you can solve a ridiculously easy puzzle (just Pound the left-hand pillar) to get some Crystal Powder and a Hard Nut. Head back to the room with the three staircases again, and take the ones on the right. Climb the ladder and follow the path around to the next room.
This puzzle consists of two parts. To solve the right-hand bit (which you should do first), Pound the two right pillars and use Move to guide the pillar into the top-left of the fenced-off ice so you can use it to Move a pillar across into a hole. For the left-hand bit, Move the pillar left, up and right, in that order. Now, climb up, use the pillar to hop across to the centre platform, Move the other pillar out of the way and go through the door.
At the end of the long path you will find an impassable ice wall. Well, it's not impassable; the three blocks form the Reveal symbol. Use Reveal and you will find there is actually a hole which you can go through. Climb the ladder to the top of Tundaria Tower. Move the pillar off the ledge and climb up and get the Burst Brooch from the plinth. Equip this on Jenna, then go down to the cracked brown section of wall at the bottom of this area, and use Burst on it. Enter, and then use Retreat to get back to the bottom. Re-enter the tower.
Use Parch on the water to the left this time, and go through the door. Go around the door on the left of this next room. In the room that follows, there's another ice wall - but this one has a crack in it. Use Burst to open up a hole, and on the other side, use the corridors to get to four chests that were previously unreachable - these contain a Slyph Feather (another form of forgeable material), a Lucky Medal, a Vial and the Lightning Sword respectively. Equip the Lightning Sword on Felix and give Piers the Mist Sabre (if his current weapon is less powerful). Now use Retreat again and run back into the tower.
Go straight ahead this time, use Burst on the block of ice and grab the Centre Prong.
Back to Yallam
You will have a lot of forgeable material by now, so go back all the way across Tundaria, to your boat, and sail back to Yallam and forge all of them. You should have enough money by now to do this. Once you're done, look back on your whole world map (R when on the world map) and find the large island north-east of the cloudy area (Lemuria - you can't go there for a while). Get off on the beach and enter Izumo.