After exploring the world with your new Airbirds, you can find new pact rings and make pacts with more spirits, and find other treasures as well.
Cave of Spirits
Go to Gnome's cave. It's east of Miguel. If you encounter Doom Gaze, you should run. Go to the northeast part of the room and go downstairs. Then go south to the next area. Go south, then all the way to the left, then north to the next area. Follow the path, then after you cross the bridge, go north and go through the door. In the room with the save point, go through the leftmost door to find a chest that contains the Emerald Ring. If Klarth/Claus equips it, his max HP becomes higher.
Go northwest to Bart's old house. Go into the northeast cave of the Long Valley, and go down the rope to reach the room that was filled with Shoki/Miasma. Follow the path and you will see a chest. It contains a Reverse Doll. From there, go down, left, and up above the bubbling pool to find another chest (Amethyst Ring). If Klarth/Claus equips it, he will be shielded from Earth. Go back to where you found the first chest, then go right and up to where there is another bubbling pool. Go down from the pool to find a chest (White Mist). Go back up to the pool, then go right and down to find another chest (Iron Boots).
Undine's Cave is on the island north of Venezzia. If the pool in the first room is empty, go through the north door, then go right and down and flip the switch.
Otherwise, go right, follow the path, go down the stairs, go down and left across the bridge, and go down, and don't flip the switch.
Go up, then left, then through the north door, then follow the path and go through the door at the end. Go up into the room where you fought Undine, and go to the top of the room to find a chest that contains the Ice Wall spell. If the right-hand pool in the last room was full, flip the switch above where the chest was in this room. Then go back out and go down the steps in the right-hand pool to find a chest (Sapphire Ring). If Klarth/Claus equips it, he will be shielded from electrical attacks.
Demitel's Island is southwest of Venezzia. Go to the chamber where you fought Demitel to find a chest that contains the spell Death Cloud.
In Thor (northeast of Venezzia), you can now go into the building to the north, whose door was rusted shut before. If you sit in front of the counter, you will learn more about the civilization of Thor.
Go to the Mother Computer and ask about Aska.
Cave of Darkness
Go to the continent northeast of Thor that is always dark, and enter the cave southeast of the city. If the cave is empty, you need to go to the Long Valley and get the Amethyst Ring, as explained earlier on this page.
Next, you should go to the Ninja Village.