Wait here is something, you do have the airship Right??
After obtaining the Cloudy Mirror in the Calm Lands, get on the Airship and go to the Macalania Woods. Go straight until you see a mother and son. Speak to them to find out that the father is late. Go to the fork (where the guards are patrolling). Take the north fork and you will see the father. Speak with him, and he will run over to the rendezvous point. Go back and speak to the couple, now without a son, until they mention the son being gone. Look around for a sparkling path and go up. Locate the north end of it (where a women was blocking it) and go to the plant at the end. Press X to examine it, and it will charge the Cloudy Mirror into its final form, the Celestial Mirror. The mirror is needed to get the Ultimate Weapons