After returning to the Airship, you must go to the Floating Continent to protect the Warring Triad statues.
Choose Your Party
When you go to the Floating Continent, you must choose three people to put into your party. I recommend Terra and other strong magic-users. The Gaia Gear armor can help against the boss, so use them on all three of the party members that you bring. This armor can be purchased in Nikeah, Thamasa, and South Figaro. Also, buy plenty of Edges/Scrolls for Shadow (Bolt Edge/Lightning Edge/Lightning Scroll, Fire Skean/Flame Edge/Flame Scroll, etc.)
107. Spit Fire
You'll be attacked on the way to the continent. These enemies are vulnerable to Lightning and Wind. You can heal up between attacks, so don't miss the opportunity to do so. You can't go downstairs into the Airship, though.
Ultros and Chupon/Typhon
When the attacks stop, go to the back of the ship, where you will find Ultros. Ultros is weak to Fire and Poison. After doing a certain amount of damage to Ultros, Chupon/Typhon will appear. At that point, stop attacking Ultros. You only need to defeat Chupon/Typhon to end the battle. He is weak to Ice and Water. Eventually, Chupon/Typhon will end the battle with Sneeze/Snort. After this, everyone is automatically healed to 100% HP and MP.
Air Force is weak to Lightning and Water. Don't attack the Laser Gun or the MissileBay/MisslBay. Just focus your attacks on its body.
Enemies on the Floating Continent
It dies if its MP becomes 0, so use Rasp on it.
Wirey Drgn/WiryDrgn/Platinum Dragon
It might use Cyclonic if it's by itself, which is devastating to your party. Try using Muddle/Confuse on it.
They are weak to Lightning. Shadow can throw a Bolt Edge/Lightning Edge/Lightning Scroll to deal a lot of damage. Gau's Aspik/Aspiran Rage works well, too.
It is recommended to equip Gaia Gears on everybody. If you do, then when Misfit uses Lifeshaver, it will actually cause damage to itself. Otherwise, attack with Fire or Holy damage.
Behemoth's attacks are all physical, so use the Phantom Esper to make everyone invisible, preventing any of Behemoth's attacks from affecting you. It is weak to Ice.
On the Floating Continent
Go down and talk to Shadow, and he'll join you. Equip him. Then use a tent at the save point that you landed near.
Note that the Charm Bangle/Ward Bangle, Back Guard/Alarm Earring, and Gale Hairpin relics will help reduce some of the difficulty of the Floating Continent.
114. Wirey Drgn/WiryDrgn/Platinum Dragon
Go east and walk up the stairs, pushing through the debris in the way. Keep following the path, pushing through more debris to the south. Keep going east until you see a blue orb. Check on it to get an item. Then go east. If you want a rare item and don't mind fighting a tough boss, go east and push through more debris, then follow the path to reach a blue orb. Check on it to fight Gigantos. You can use the Phantom Esper to prevent Gigantos from hurting you. You can try using Shoat/Catoblepas to kill it instantly. Or you can cast Bio on it. After you defeat it, you get a weapon for Shadow called Hardened/Sasuke.
After defeating Gigantos, go up to the platform that is to the right of the first blue orb that you saw on the Floating Continent. Stairs will form. Walk onto the platform and it will transport you to a location to the southwest.
After you have teleported, go all the way south, then go slightly east and step on the switch in the ground. Then go east, and go down only one flight of stairs, then go east until you reach another teleporter. Use it.
Go south and use the teleporter to the left. Step on the switch at the bottom left, then go north and step on the switch up above. Go south from the stairs and go west where the ground just moved. As soon as you see stairs, go south down them, and then go south down a second flight of stairs. Then go east, and after going north up three flights of stairs, go east.
Ignore the northwest switch, and go southeast, then east to find a blue orb that contains an item. Then go south to find another teleporter. Step on it to go into a room where there is a save point.
After using the save point in the room, go northwest and step on the switch, then use the teleporter that was revealed.
Go south and you'll be given the option to jump back onto the airship. If you do, then you will have to do the entire Floating Continent again the next time you go to it. However, this can be a good option if you want to switch characters or stock up on supplies, or if you just want to use the Floating Continent to level up. But Shadow will stay on the Floating Continent, so you can't level him up if you go to the Airship.
If you're ready for a boss battle, go west from the Airship, push the debris out of the way, then go north fight AtmaWeapon/AtmaWepn/Ultima Weapon.
AtmaWeapon/AtmaWepn/Ultima Weapon will die if it runs out of MP, so use Rasp if you can. It helps a lot if you equip Gaia Gears, because if AtmaWeapon/AtmaWepn/Ultima Weapon uses Quake, it will heal you. AtmaWeapon/AtmaWepn/Ultima Weapon uses primarily magic attacks, so you can cast Safe/Protect or Rflect/Reflect to help defend yourselves.
After the battle with AtmaWeapon/AtmaWepn/Ultima Weapon, go north to see a cutscene with Kefka and Gestahl.
When the timer starts, be sure to equip Celes if she was not in your party before the cutscene. Then make sure you have Sprint Shoes and the Charm Bangle/Ward Bangle equipped. You will be attacked by Naughty/Naude on the way. It is weak to Fire, Lightning, and Holy attacks. It can also be killed by bringing its MP down to 0 with Rasp, or by casting Imp on it to make it flee the battle.
Run east, then go northwest when you can. The next time the path splits, go east. If you want to open the blue orb near the end, DON'T walk up to the stairs from the left. Go around and walk up to them from the right. Then go east to the sparkle and check on it. You will have to fight Nerapa/Nelapa.
Nerapa/Nelapa will cast Doom/Fiend on everyone at the start of battle. Nerapa/Nelapa has Rflect/Reflect on itself, so magic will not work on it unless your party members have Rflect/Reflect on themselves, allowing you to cast the magic on them, making the magic bounce off and hit Nerapa/Nelapa instead. It is weak to Ice, Lightning, and Holy. Otherwise, just use physical attacks.
After the battle, go east. When you reach the far right edge and are given the option of jumping onto the airship, choose to WAIT!!! Then when the countdown reaches 0:05, Shadow will return. If you don't wait, you will never get Shadow back for the rest of the game.
After Shadow rejoins you, watch the cutscene. Gameplay will resume on a small island.