Alistia is an ocean planet that is unlocked after you get at least one of the key pieces in Chapter 8. The planet is entirely optional and the events that occur on it don't have a large impact on the storyline.
Watch the cutscene as the Dorgenark lands in Alistia. After you have control of Jaster again, teleport to the Deck from the Control Room and make your way off of the ship. Activate the teleporter and save if you wish. Then follow the tunnel round to end up in a village.
Directly in front of you when you enter the village you will see a shop with a chest in it. Open the chest to gain a Captain's Sock. Feel free to buy some supplies in the shop. Just outside the shop you will see a set of stairs. Ascend these to come across 4 chests containing 2 Max Heals, an Alluring Lamp and an Izerium Alloy. The Sun Key is needed for one of the chests. Make your way down to the beach area and open the chest containing a Phantom Slayer, a sword for Jaster. Make your way down to the opposite end of the beach, passing the teleporter and activating it, to come across a chest containing a Prominence Shield.
Once you have opened all of the treasure chests in the village, make your way to the house at the very far end to trigger a cutscene.
Once the cutscene is over head to the teleporter, near where the Prominence Shield was, and go through it. Follow the path leading to an elevator. There is a chest near the elevator which contains a Silver Bangle. Take the elevator up and directly in front of you, you will see another chest containing 2 Sealing Sunspheres. Now follow the pathway round.
Before crossing the bridge, go to the right as there is a chest containing a Mirror Unit. Backtrack to the bridge now, and cross it.
After crossing, go left to open a chest containing an Ice Shield. Follow the path to a ledge where you should jump down to the left. If done correctly, you will land on another ledge with a chest on it. Open the chest to gain an Opinicus EX, a bow for Lilika, after that jump off the ledge. Take the path down to end up at a big opening.
Take a left when you reach the area with a big opening. You should come a cross a chest containing a Nebuladon Egg. Backtrack a small bit and traverse through the wide space. You will come across a chest by a palm tree containing a Lupine Launcher, a missile launcher for Simon. Keep going the way you were heading after the chest and you should come across a shop. Feel free to stack up on supplies again. Straight ahead of you, you should see a teleporter, activate it and save your game.
There will be a choice of taking an uphill path or a downhill path here. Take the uphill path and grab the chests containing 3 Tri-Heals. The other chest has a Zhen trap in it so be careful when opening. It contains Despera Tonfas, daggers for Kisala. Follow the path and keep close to the inside wall. You will notice a gap in the wall. Go through it and take the Star Earrings to you right. Go to the very edge of the ledge and jump to the ledge directly in front. This can be annoying as if you don't time your jump right at the edge you will most likely slip and follow all the way down and have to make your way back up. After landing on the ledge you will have to another ledge directly in front again.
On this ledge, there are 3 chests containing, a Spirit Chorus, a Spear for Jupis, Succubus Slippers, some footwear for Kisala and 2 Excelion Shards. Now jump down from this ledge to end up on downhill path. Follow it and at the far end you will see a chest containing a Nebuldan Egg. Take it then continue to follow the path until you reach another teleporter. Save your game.
Open the treasure chest in this area to fight a Mimic if you wish and there is another chest which can only be opened with the Sun Key. You will notice you can either go right or left here. Take the left path first. Follow the path and don't forget to take the 3 Tri-Charges along the way.
As you follow the path you will notice a downhill slope leading to a bridge. Don't cross it yet. Go to the ledges above the bridge. On one side you will see a chest containing a Dark Music Box and on the other you will gain a Lunar Ribbon and 3 Heal Potions. Now go down and cross the bridge. This will lead to another tunnel which you should go through.
Once you are through the tunnel you will notice a chest containing a Stamina Extract. Take the path up the hill to end up on a small platform that overlooks the sea. You will notice another pathway leading down besides the one you took up. Take that path.
Now you will come across which seems to be a long sandy path. Follow the path round and fight the Mimic in the first treasure chest and then take the 3 Recharge Drinks in the next chest. You will come across a grassy area with a teleporter on it. Activate it and save if you wish.
You will notice that you could have continued on the sandy path and through some submerged sand but going this way leads all the way back to the teleporter where you chose to go left instead of right. All that is on this path is a Mimic and 1 or 2 chests. If you want to see what is on this path take the teleporter back to the grassy area once you are finished.
You will notice a crack in the wall with a ledge on one of its sides. Jump up on the ledge and jump to the next one after that. Follow the ledge round to gain a 2 Perfect Revivers and then follow the ledge the opposite way to get a Hyper Crystal and 2 Divine Protections. Drop down from here and take the chest behind you to get an Electric Eel. A cutscene will be triggered when you start following the path.
After the cutscene, follow the path to come across yet another tunnel. When you enter the tunnel a cutscene will trigger.
Follow the winding tunnel round. There are no enemies here. You will come across some makeshift stairs, ascend them and activate the teleporter. This should mark that you have activated all of the teleporters in Alistia. Save here and teleport back to the village if you think you will need to stack up on supplies, as there is a boss battle coming up. When you are ready follow the path to get outside the tunnel.
Alistia Ocean Laboratory
As soon as you enter this area a cutscene will trigger. After the interesting cutscene, you will be up against a boss.
This shouldn't be too hard as the bosses attacks aren't all that strong but you might have to heal at some points. Its only weakness is its head and it attacks with its pincers. Buff your members with whatever buffs they have and then attack the boss head on. When its health goes down a bit, it starts to jumps away and it will start firing missiles at you. These aren't that hard to dodge. When the bosses health gets to about halfway a cutscene will start.
After the cutscene you will be back fighting again. Use the same tactics you were using in the first half of the battle. This time feel free to use your strongest attack abilities in order to do some damage. Watch out for when it jumps away again because this time it will either shoot missiles or it will run at you, causing a lot of damage to any character it hits and a high chance of killing them. The plus-side of this fight is that the boss will only have half its health left. It shouldn't be overly hard to destroy the remainder of its health.
After the battle, you will end up back in the village and you will receive one of Jaster's alternative costumes, his Pirate Costume.
After this happens, you are finished with Alistia and can continue on from where you left of before Alistia.