Before going to Moria, you seek a contract with Ifrit.
Go to Alvanista and buy supplies. Get at least six Rune Bottles.
To reach Ifrit's cave, go east from Alvanista, then south to a dock. Take the ship to Freland. Once there, go east, and enter the village first.
Walk up between the upper-left houses to find a chest (2,600 gold). Go to the south entrance of town and walk east to find another chest (Mixed Gummy).
In the item shop, buy two Silver Capes and use a Rune Bottle on each to turn them into Princess Capes. Equip them on Mint and Arche. Use a Rune Bottle on a Mantle or Aqua Mantle to turn it into a Flame Mantle, and equip it on Cless/Cress. Equip Klarth/Claus with the Garnet Ring. This gives everyone protection against fire.
Buy Remedy Bottles at the Pharmacy.
Equip Cless/Cress with the Ice Scimitar that you won after battling Meia. It works well against the fire enemies in the next area.
Change Arche and Klarth/Claus's tactics to cast many spells. Turn off all of Arche's fire spells, have Klarth/Claus ready to summon Undine if he has it, and don't equip Cless/Cress's Phoenix skill if he has it.
Go east of the city to find Ifrit's cave.
From the entrance, go to the right and up to find a chest (Spy Lens), then go straight down and down the stairs.
Go down from the stairs to find chests. The one on the left contains a Talisman, and the one on the right contains a Resist Ring. From there, go left and up to get the Sorcerer's Ring. Equip it on anyone in your party and use it to shoot sparks. Now go back up the stairs.
Go all the way to the left to find a locked door. Walk on the column in the lava until you are facing the switch in the wall. Use the Sorcerer's Ring to hit the switch and open the door.
Go up and left to find chests. From right to left, they contain a Savory, a ?Weapon that becomes Thunderclap, and a Battle Rune. Equip the Battle Rune on Cless/Cress now. From there, go down, and go down the stairs. Follow the path.
When the door is locked behind you, go up the stairs to find chests. The bottom-left one contains a Mixed Gummy, the upper-left one contains 1000 gold, and the one on the right contains the Magma Key. Then go back down, then go right and down. You will be back in the room where you got the Sorcerer's Ring. Walk right and go up the stairs.
Now go left and through the door that you see. From there, go left, open the chest (Charm Bottle), and use the Sorcerer's Ring on the switch on the back wall. Go back to the save point and up through the door.
In the next room, check on the locked door to use the Magma Key. Go up and you will see some columns. Some of the columns are standing up. Use the Sorcerer's Ring on the columns that are standing up, and they will fall, giving you a path through the magma. Go through the room this way to reach Ifrit.
Cless/Cress should not use Phoenix. Otherwise, he should use his best skills.
Ifrit's Cave, Part 2
Open the chest behind where Ifrit was. It contains Fire Wall, a spell for Arche. Disable that spell for now. Go into Klarth/Claus's skill menu and disable Ifrit.
Go straight down to leave Ifrit's Cave.
When you are out of the cave, you can change Cless/Cress's weapon if you wish. Change Klarth/Claus and Arche's tactics to not cast spells, but re-enable their fire spells.