You can then earn another 60 by completing the Chocobo Race at Remiem Temple with five chests collected. These 120 Three Stars should be enough for all your needs (though you can only carry x99 at a time, so use ‘em before you lose ‘em). That said, if you really need more then you can farm Catoblepas at the Monster Arena. It has a single Three Stars as its common drop (~80% chance). Or if you have enough money, you can bribe Behemoth Kings with the ridiculous sum of 1,687,500 gil for x14 of these Three Stars. If you’re interested in farming for drops, Catoblepas will be unlocked after you capture one of every fiend on Mt. Gagazet. The list is as follows:
Bandersnatch Grat Bashura Grenade Splasher Achelous Maelspike Ahriman Grendel Mandragora Behemoth Dark Flan
Or if you’d rather try bribes then Behemoth Kings can be found inside of Sin.
Three Stars Uses
Using a Three Stars with the “Use” command in battle will reduce the party’s MP costs to zero for that battle. Pretty handy. You can also use them to customize the One MP Cost and Break MP Limit abilities onto weapons and armor, respectively. Or you can use Three Stars to teach any Aeon Doublecast.
One MP Cost requires x20 Three Stars Break MP Limit requires x30 Three Stars Doublecast (Aeon) requires x5 Three Stars
Rikku can also mix up some Three Stars with her Overdrive, and here’s a few handy ones to consider:
FreedomX (Hypello Potion + Three Stars): Reduces ability MP cost to 0 for the party.
Supernova (Blessed Gem + Three Stars): Deals an extreme amount of non-elemental damage to all enemies.
Miracle Drink (Designer Wallet + Three Stars): Drastically increases critical hit rate for all party members.
Is It Worth Farming Three Stars?
No. Anybody who would really benefit from One MP Cost (namely Yuna and Lulu) will already get that ability from their Celestial Weapons. Also, Break MP Limit is a useless ability, considering you’ll never need that much MP – and considering how easy it is to recover MP as the game goes on. MP is an important thing, of course. But you’ll never need more than 999 of it. The best thing to do is to keep all those Three Stars in your inventory to use in Rikku’s mixes.