Go to the dream world during a full moon by falling asleep by the hearth in the cabin. When you first see the Grizzled Boor, follow him to the titanic tree and enter to fight him. After defeating (but not killing) him, take the key and return to the 'real' world. Go past the wall blocking the road to Mingi Taw, cross the stolid log bridge, and in the next area is a hidden door below the trail. Use the key to open the door. Once inside, you can manipulate the 'moods of the moon' at the bench.
Summon the Sylvan Sprites
Follow the instructions below:
Perilous Precipice: Play the Song of Sworcery at this point and interact with the rainbows.
Stolid Log Bridge: Play the Song of Sworcery at this point and interact with all of the trees by the river.
Sheep's meadow: Play the Song of Sworcery at this point and interact with the sky above the stick overlooking the meadow.
Check your Megatome for hints when you're unsure of what to do. Often the thoughts of other characters provide clues as to your next task.
When blocking consecutive enemy attacks, remember to press the shield button again. If you hold it down, the second attack won't be blocked.
Use psychedelic mushrooms to see secrets in the surrounding environment. Collect some by looking for glowing pixels on the forest floor.
To regain health, remember to hold the shield button during combat. This will give you health back, albeit slowly.