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. If you encounter Doom Gaze, you should run. Go to the room where you flipped the switch that started the alarm. Go through the leftmost door to find a chest that contains the Emerald Ring.
Go into the cave of the Long Valley, into the room that was filled with Shoki, by going down the rope in the hole at the far right of the cave. Follow the path and you will see a chest, which contains a Reverse Doll. From there, go down, left, and up above the bubbling pool to find another chest (Amethyst Ring). 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 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 and through the door, then follow the path through the door. 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).
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 door that was rusted shut before. If you sit in front of the counter, you will learn more about the civilization of Thor.
Have Arche ready to cast Indignation, and have Klarth ready to cast Volt. Go to the Mother Computer and ask about Aska.
Cave of Darkness
If the cave is empty, you need to go to the Long Valley and get the Amethyst Ring, as explained earlier on this page.
Northeast of Thor, the continent where it is always dark has a cave southeast of the city. Go there.