What do you use the sigils for on Final Fantasy x?

Answer 1

the sigils are one of the ingredients in unlocking the true power of the ultimate weapons, each sigil has a corresponding crest ie. moon sigil, moon crest. these items can then be taken to the macalania woods, at both ends of the forest is a silvery pathway that leads up to the trees, there is then a a type of shrine you can use the sigils and crests you've obtained with the ultimate weapons, however to obtain the ultimate weapons or use the shrine you need the celestial mirror (formerly the cloudy mirror, which you get from beneath the remiem temple if you win the minigame with the chocobo)