Find... Energy crystal
Find it These crystals can be found in the Pride Lands and, sometimes, Hollow Bastion. Bookmasters and Shamans have a habit of dropping them. They aren't used in many recipes
Find... Frost crystal
Find it If you're after one of these you'll need to pay a visit to the Pride Lands. The strangely-named Living Bone monsters have them, who are often ridden by Shaman Heartless.
Find... Lightning crystal
Find it Another item that can only be found in one world, this time Space Paranoids. They're dropped by Strafers and Devastators and are used to synthesize power boost recipes.
Find... Dark crystal
Find it These things are dropped by Air Pirates, but only in The Land of Dragons, Mulan's level. They're one of the key ingredients in the magic boost recipe, which increases your maximum AP.