You have to get the Sun crest and Sun sigil to power up the caladbolg. Walk around macalania forest and find some people separated from their family. Reunite them and they'll move out of your way in front of this great big seed plant looking thing on the celestial looking starry road that goes up over teh forest and has no encounters. Go up to that plant thing and it'll allow you to upgrade your celestial weapons if you have the appropiate sigils and crests.