In Malcalania Woods, there is a person who will explain to you the Butterfly Catcher Sidquest. The goal of this sidequest is most likely to obtain the Saturn Sigil, which is needed to obtain Kimahri's Ultimate Weapon. Talk to the person who explains the minigame and after that, find the closest Butterfly and touch it. A Timer will appear and them you have to catch 7 blue butterflies before the time runs out to complete the minigame. For every Red butterfly you touch you'll lose one second off your Timer and you will be forced to battle.

Once you collect 7; a chest will appear and a prize will be inside. If you attempt to do the Butterfly Catcher Minigame again, time will lower and it will be more diffcult. Once you return with the Airship, there are increased amounts of Red Butterflies, again, complete both areas and then you'll recieve the Saturn Sigil as the prize.