First you will need the Cloudy Mirror, which can be won for the Chocobo Race in the Remiem Temple. Talk to the women in South, Macalania Woods and she will replay, that she is waiting for here husband. Then go to the Campsite and you will find him there, talk to him and then he would go back to his wife. Once you return where his wife is and keep taking to the couple until they say that their child has gone missing. Walk up the Crystal Path and you will find the boy. Talk to the boy and examine the large crystal, then you will receive the Celestial Mirror.

Celestial Mirror - Caladbolg - Nirvana - Masamune - World Champion -
Spirit Lance - Onion Knight - Godhand