The Sealed Temple is south-west of the Phantom Village. It is beneath the ocean and therefore can be accessed as soon as the submarine is acquired. On your first trip (before defeating Neo Exdeath) you can acquire the Gladiator, Oracle and Cannoneer GBA-exclusive job classes. However, come back after beating Neo Exdeath and the fun really begins. You can now press the switch in the centre of the room, moving the room and allowing entry to the Sealed Temple.
The first area is called ??? and consists of a savepoint and door into the next area. Use the savepoint! You will be coming back here a lot and you will be using it a lot, for good reason.
The first proper area of the dungeon resembles the Dimension Castle in the Rift. Most of the encounters are familiar too, though the group of 5 Dark Grenades are annoying simply because they are difficult to take out quickly with Rapid Fire. If you have the gil, you may wish to give !Zeninage to someone, or Dualcast Syldra while wielding the Air Knife. Syldra is Wind-elemental and therefore has his power boosted by the Air Knife.
The area is fairly simply. Head south until you arrive at a pair of double doors; these are locked at the moment so head to the right and enter the Ruined Shrine. Here you can meet Assassins - they have high evasion and can cast Image. Follow the corridor and head south at the first junction. Take the warp on the left, and you will arrive in Titan's Grotto next to a treasure chest containing Dark Matter. Head all the way to the right and down the stairs to find a chest containing an Elixir. Head all the way back to the left, drop down the waterfall and head left to find the Vishnu Vest, and piece of armour that halves damage from fire, ice and lightning attacks.
Now you can follow the path to the right again. The encounters in this area consist of more enemies you've met already in the Rift, such as Iron Giants and Yojimbos. Eventually, the path leads to a door to the next area.
This area is filled with a new enemy; the Behemoth. Like King Behemoths (which are weaker than Behemoths...) they counter all attacks with one of their own. However, they have one last trick up their sleeves - when the die, they cast Meteor, which will likely hit your party for lots of damage. There are two ways around this. First, to progress in the Sealed Temple you will need to Catch a Behemoth, so while you should definitely Catch one, you could Catch them all (which will be much easier with the Kornago Gourd). The second option is to sap their MP with Spellblade Osmose, and then finish them off.
Head down the first set of stairs to find an Elixir. Then head back up and to the right, and follow the linear path into the next area, the Hall of Watchmen. Head all the way to the right and take the warp to the River of Souls; we cannot do anything to the north yet. The encounters in this area include Mindflayers, Mecha Heads and Level Trickers, so nothing you can't handle.
In the River of Souls B1 there are three treasure chests; Iron Draft, Goliath's Tonic and Power Drink. If you intend to use them, you will probably have bought 99 already, so I would not bother collecting them. In the River of Souls you can encounter various difficult enemies, including the Ruhk and the Vilia.
Follow the path, avoiding all the stairs leading into the water, and take the door to B2. Again, I do not consider the treasures worth collecting (an Elixir, Dark Matter and Turtle Shell), so head to the right and follow the narrow corridor. About halfway down the corridor a purple palette-swap of Ghido stands in your way - the Gil Turtle.
BOSS - Gil TurtleEdit
As with in the cave on Galuf's world, the Gil Turtle has 32,768HP. However, here, we can do a couple of things that we couldn't do the last time (if you even fought him). First of all, cast Mighty Guard, as Protect and Float are essential for the fight. The Gil Turtle begins with Protect and Shell, so with your White Mage, cast Dispel on him. You will also want to summon Golem and cast Hastega.
Now you can attack him. Dualcast Blizzaga and use Blizzaga Spellblade with Rapid Fire and you can deal heavy damage while Golem soaks up the counterattacks. If you are wearing shields and elven mantles like I normally do, this will also increase your chance of evading the Gil Turtle's attacks. As we can Dispel him now, he will take much more damage from your attacks and should fall fairly easily.
Now we can continue to the River of Souls B3. Encounters here include the Stingray and Movers. Head to the right to find a Cottage (if you still need it) and then head back and follow the path to the left. All the way to the left is a chest containing a Fuma Shuriken. Then head to the north, where you will find a man asking you to catch a Behemoth. If you've done this already, he will unlock the doors you passed in the entrance to the Sealed Temple.
With the doors unlocked, head all the way back to B1 and leave the River of Souls through the door you arrived nearby. You will arrive in another Ruined Shrine area. Follow the path and you will pass three locked cells, one of which contains a demon that looks like Twintania. We can't let him out yet, though. On the left side of the cells, you can find some secret passages leading to a Blastshot and a Buckshot.
Continue and exit the area. You will arrive at the left door in the entrance area. Head back north, use a Cottage, and save your game, before continuing to part 2 of the walkthrough.