In the Shrine
Use Lash on the rope, and basically go all the way back to where you got Breath the Jupiter Djinni the first time. Go to the left from here, use Frost on all the puddles, then jump across and through the door. You'll have to navigate a long but easy chain of pillars here, then go through another door. In this room, go up and descend the ladder. Go down to the bridges at the bottom, and walk to the right until one cracks, dropping you. The current will carry you to a stop. Now head down and around, then up the ladder to get a Rusty Staff from the chest. Use Lash on the rope, then go back up to the top. Walk on the cracked middle bridge and let the current carry you down to the rocks. Get off and go up the ladder and through the door.
In this room, go down the ladder and move the pillar across to the hole to open a shorcut. Climb up the ladder and descend the stairs. Hop along the rocks to reach a Reveal symbol, where you should use Reveal and hop across. Use the Sea God's Tear on the statue and it'll flood the cave, carrying you up a level.
Climb the ladders up to the very top of the tower, and grab the Right Prong from the plinth. For the mean time, this is useless - you will need the Centre Prong and the Left Prong. Go back down to the statue and use the Sea God's Tear again to descend. At the bottom, use Retreat to leave the Shrine.
Beginning the Trading Quest
At this point you can and should start a side-quest that will allow you, eventually, to get the Catastrophe Summon, which is very powerful. You can't finish it at the moment because you're Psynergetically incapable (hey, a new word!) but this guide will tell you when you can come and finish it (which is not until the end of the game, incidentally). So, get back on your boat and search your world map (R button) for a snow-covered island roughly southeast of Garoh. This is where you want to go, so sail there.
East Tundaria Islet
A single family, and for some reason, a Healer, are the only people who inhabit this island. The blue jar to the left of the house contains a Lucky Medal. Now, set Mind Read to a Psynergy Shortcut and mind-read the penguin. You'll find out that his girlfriend has hurt her leg and is trapped on the other side of the water. So, hop across the moving ice blocks and push the log off the cliff at the top. Go down the groove to the right, then cross the log and push (you can't Move) the female penguin across (you can get the Psynergy Stone as well). Once she's back across, the male penguin will give you a Pretty Stone for your troubles.
SE Angara Islet
Leave East Tundaria Islet, and sail all the way northwest to the island just off the coast of Angara. Here, check the square box on the raft to the right for a Lucky Medal. Go up the stairs to the top box, and Move it off the cliff. Go back down and Move it until it's underneath the bit where you can push the other box off. Go back up and push the other box off so it lands on top of the other one. Go down and freeze the puddle with Frost, then jump across and climb the vines. When you approach the nest, the bird flying around will come back. Mind Read it, and give it the Pretty Stone. You'll get the Red Cloth. Although you won't be using it for a while it is very important that you do not sell this.
Leave SE Angara Islet, and head to the southeast of Osenia. There's a beach split by a river here - get off on the west side of the river. Follow the path all the way north to a small town called Yallam.