Chests (5):

• Reflect Mail
• Black Belt Gi
• Chakra Band
• Rune Bell
• Faerie Claws

Just follow the maps, collect all treasures. At the end, you will be able to board The Invincible.

It is a larger airship that has a ability to fly over small mountains (you still cannot fly over any mountains though). Now that you obtained The Invincible, you can check your progress any time without going back to Gysahl.