Instructions
Travel to Cassia. Leave the ship and talk to the dwarf standing near where you land. He will explain he needs a special item called the Aquarino in order to upgrade your ship so you can travel to the fire planet. He will tell you that you can get it from the otters at Port Pescado.
Go to Port Pescado. You will be stopped by a police officer who will forbid you from going into town. Keep talking to the officer and the detective will show up and allow you to go though. Follow the detective and he will ask you to help him carry out a plan. Wait for him to distract the guards, then move past the guards and to the next area.
Keep following the path until you see a wall covered in vines. The detective will catch up with you just in time to fight a boss named Chard who is also after the Aquarino. Defeat the pirate otters first, then focus attacks on Chard to defeat him.
Use fire magic after the battle to burn the vines on the wall. This will reveal a door. Go inside and you will see a rock with a plant growing out of it. Use wood magic to make the plant grow into a tree, which will break the rock and open a door where the Aquarino is located.
Return to the dwarf you spoke to near your ship. Give him the Aquarino and he will attach it to the ship, allowing you to leave and travel to the fire planet.