The White MaskEdit
At Fynn, it's shopping time. Buy Dispel and Slow at the magic shop and a pair of Wing Swords for Leila, but leave the Ancient Sword on Firion (Curse kicks ass). Also, rest at the Inn in the center of the town. Then, go to Paul's House (the southeast-most house) and ask him about Ekmet Teloess. He'll give you some directions for the secret passage: far corner of the audience chamber, to the right of the throne.
Go to F4 of Castle Fynn and go to the right of Gordon's throne. The passage is right there. You'll be on a long staircase that heads to Fynn Castle Dungeons.
On B1, go north and get in the northwest corner to find a chest with Eye drops, then head east to find the stairs leading down. B2 is even more simple: go northeast and grab the ether in the chest, then go west near the stairs and follow the first path you see heading north and go down the stairs.
B3 is a bit more complex. Head southeast to find a Hi-Potion, and then go to the southwest corner and grab a Flame Shield. Now, head to the northwest corner and grab a Spider's Silk, then go south and you'll find the staircase leading to B4, where you just have to get to the southeast corner and descend the stairs.
B5 is confusing. Go east until you find a piece of land and you'll face two paths leading north. Take the left one and it will lead you to a chest holding an Orichalcum: the second best dagger on the game! Equip it to Leila right now! Now, go north and you'll find a LOT of doors. Get on the 5th door, counting from the left. You'll find the White Mask's altar. Get on the teleporter and go out.
Talk to Hilda and she'll ask you to take the White Mask to Mysidia. You should know the way by now, but it's south of Altair and east of Palamecia Castle. Once there, go to the other side of the central lake and go to the island on it's center. Descend the stairs and inside the dungeon there is a statue. Use the White Mask with the statue and leave. If you have the money, get Holy for your White Mage and damage dealer.
The Black MaskEdit
Leave Mysidia and get on the Ship. Use the Map and search for a Tiny spot on the middle of the sea -- that's your next destination, the Tropical Island.
By this time, your party should be above 1500 HP, save Leila. Your spells should also be at least at level 6.
When you reach the Island, enter the cave. This is the only dungeon where I recommend Warp. You will probably level it to level 3 in this dungeon. Anyway, Warp is superfluous in any other dungeon.
Inside, go south until you grab a chest with Eye drops, then turn back and follow the west path when you see one and go south to a path that leads to a chest with an Ether. Go back to the path leading West and now go north when you can and follow that path to find the staircase.
B2 in easier than B1. Go north until you see a stair case an grab the chest with Sleepgrass. If you go down the stairs, they will lead you to an area with a chest containing Spider's Silk and another stair case that leads to B4. B4 consists on a small path that leads to a staircase going up. Use it, and you'll be at Tropical Village! There, you will only find masked weirdos. The Green masked ones sell stuff! Too bad that they sell colossal crap, except maybe for Gaia Drums. Buy a handful of them for an emergency.
Go back to B2 and now go east from the staircase that lead to Tropical Village. Grab the chest with a Scourge Tome and head south. On the south-eastern corner you will find a chest with a Blind Tome. Return to the path and you'll find a chest with another Scourge Tome. Keep them. Now, follow the path once again and you'll find another Blind Tome inside a chest on an alley to the left. Go North and you'll find the staircase leading to B3.
B3 is much easier than B2: Go south and you'll see a chest with Garlic. After that, go north and continue through the path to reach the stairs.
B4 is big. Go north from the Stairs and you'll find the stairs leading to a small cubicle on B5 that contains a chest with a Death Idol. Go back to B4 and now head south-east until you reach the corner with some stairs leading up. On that section of B3, go north and you'll find another staircase, but this one leads to B4 again. Back on B4 go south and you'll reach a staircase that leads to a section of B5 with three chests: two Sleepgrass and a Gaia Drum. Return to B4's main area, and head through the north-east path and there is a chest with 1000 Gil on a small alley. Continue heading east and you'll reach B5.
On B5, grab the chest near you to receive a Sleep Tome and enter the room to the west. You'll find the Black Mask's Altar. The Black Mask is guarded by a beast. Heal yourself and save, then hack at him!
Grab the Black Mask inside the chest and get inside the teleporter. You are now outside the cave.
Now, go to Mysidia and there you will learn at the library that you must use your Black Mask with a doppelgänger. If you talk to the mages, you will also learn that the Crystal Rod, an item that grants the entrance to the Mysidian Tower lies on a cave on the Mysidian continent. Leave Mysidia. Your destination is a cave to the east of it.
Soul of Rebirth