This relic turns all MP used on any magic move to only 1 MP. You can only get it the second world, after Kefka blows up the world, above the Veldt (the place where you teach Gau new moves). It is a small forest patch on the island just north of the Vedlt Island. You will be close when Tyranos start attacking. Keep fighting them and every once and a while a monster called a Bracosaur will attack. Have Locke steal from it. If that was unsuccessful, kill it and hope that it appears after the battle.