Enemy list
Chest list
Board the airship and walk to the steering wheel on the far right. Fly east and land just south of Castle Sasune. The castle has 13 chests split across two towers and the main keep; the Sealed Cave north of here has 5 more.
Castle Sasune
Enter the castle and go left through the doors to the western tower. Climb to 3F where Chest 1 (Holy Arrow, 23/367) is on the left and Chest 2 (Hi-Potion, 24/367) on the right. On 4F, Chest 3 holds a Wightslayer (25/367) but opening it triggers a Griffon (#037) fight. It hits hard for this point in the game, so heal up before you open it.
Cross the courtyard to the eastern tower on the right. Climb to 3F for Chest 4 (Eye Drops, 26/367) and Chest 5 (Antidote, 27/367). Go up to 4F for Chests 6, 7, and 8: Phoenix Down (28/367), Bow (29/367), and Wooden Arrow (30/367). There's a bed up here; rest if you need to.
Back in the courtyard, go south and left into the main castle. Take the stairs up to 2F and go left, then left again through a hidden wall behind a banner. When you hit the bottom wall, turn left and follow the hidden path around to stairs on 3F. The path leads to Chests 9 and 10: Leather Shield (31/367) and Blizzard (32/367).
Walk along the first hallway and through the banner. Between two statues there's a secret passage to Chest 11 (Tonfa, 33/367). Double back to 2F, take the passage north and down the stairs to 1F for Chests 12 and 13, both 1000 Gil (34-35/367). That's all 13 chests in the castle. Back out and leave.
Go to your airship and fly north. Land just above the water and you'll see a cave entrance.
Sealed Cave
B1. Walk south and open Chest 14 (Potion, 36/367). Take a right and follow the path north for Chest 15 (Cure, 37/367). Continue south to B2.
B2. Pick up Chest 16 (500 Gil, 38/367), then go northeast and talk to the skull to open a passage. Sara is inside; she joins your party as a guest (she won't fight but helps with healing). Take the stairs down to B3.
B3. Go south to the bottom of the map for Chest 17 (Antarctic Wind, 39/367), then turn around and follow the path north for Chest 18 (Eye Drops, 40/367).
Check your bestiary for all 6 entries before moving on. You can come back to this cave later, but you'll be teleported out after the boss fight; saves a trip if you grind now.
How to Beat Djinn
After the fight, Sara seals the Djinn away and teleports your party to the wellspring room in Castle Sasune. You'll end up in King Sasune's throne room. Speak to him and he'll hand you a Canoe.
Back to Kazus
Leave the castle and walk north toward the cavern. Use the Canoe to cross the lake and get back to your airship. While on the water, you'll run into 3 new bestiary entries: Killer Fish (#031), Hermit (#032), and Sea Elemental (#033). These sea enemies may become unavailable later in the game, so tick them off now.
Fly to Kazus. Cid greets you at the entrance and joins your party. But before you leave town, go to the northern edge where there's a cave: the Mythril Mines.
Not much to this one. Go north and hit the button on the wall to open a secret path. Walk through to B2 and grab Chests 19 and 20 at the dead end, both Mythril Swords (41-42/367). The same enemies from the Sealed Cave spawn here (minus the Revenant).
With the curse lifted, all the shops in Kazus are open now. Mythril equipment and new spells are available, so upgrade your party. Talk to Cid and he'll tell you to visit the blacksmith in the northernmost house. The blacksmith installs a Mythril Ram on your airship, which lets you smash through the boulder blocking your path west toward Canaan.