Temple of Fire

Start by opening the chest to the west that contains a Flametongue. The temple has the same layout as the Water Temple so you can go ahead and collect the items first while inspecting the empty rooms to view some scenes. There's also the anchorite of fire, mouthpiece of Promethean Fire in a small room to the southeast.

The chest to the southeast corner of the temple has the Iceflame Shield, the two to the northeast contains an X-Potion and Turbo Ether. The last chest is a hidden one located behind the walls to the west. Follow the hidden passage to get an Elixir.

Make sure everybody's healed. You need to have at least one Salve-Maker, preferably with white or black/white support in your party. His/her Healing Lore, Compounding and Widen Area skills will be pretty useful in the upcoming battle. Save your game again and enter the altar.

Boss: Chaugmar

HP: 40,000 Weakness: Lightning, FAM: Demon

Chaugnar has move that will steal HP, MP and even BP. That said, it will be risky to stack up BP like you normally do with the other bosses. When it is covered with energy, it will be resistant against any type of damage, even when hit by its elemental weakness. This is where you have to compound items or use the attack items as is. Like the other bosses, you have to use Default once you see it has positive BP. Play defensively when it is in its invulnerable state and heal up any damage you immediately receive.

Hopefully, your stacked BP won't be stolen during the boss' previous attack; use the stacked BP to executive extra actions while the boss is in vulnerable state. Be careful of its Energy Burst as it can knock out several characters at once. If not, your characters will have critical HP. With the Salve-Maker's Healing Lore and Widen Area, you can use an X-Potion to heal 3000 HP to all your characters. Same goes with Phoenix Down that can resurrect multiple characters. Since the boss has the tendency to drain your MP, an Ether deployed by the salve-maker's Widen Area is very effective and efficient. Your current White Magic spells won't be able to match these potent recovery options at this point.

After the battle, you'll receive a Reflect Ring. You'll now have to perform the same ritual to awaken the Fire Crystal. Your ability cost limit will also increase by one after the ritual. Once done, leave the temple and use the shortcut to return to the Mythril Mine. You now have to report to Commander Goodman in the Eisen Bridge. There's also a new sub-scenario available in Starkfort. Refer to this link for more details.

After reporting to the captain, return to Hartschild. After arriving to town, bring Egil to the Goodmans. After the scene, a new party chat will be available (Wary Airy) Rest at the inn and leave the town. Your next destination is in Grandship.