Premium currency

Master currency is a recurring element in select Final Fantasy mobile games. For titles that use master currency, it operates over and above any other currencies used, often being difficult to earn and in many cases also being purchasable from within the game itself. Titles that offer master currencies, therefore, may also permit the exchange of real-world currency so as to obtain them.

Final Fantasy Record Keeper
Gems, also known as Mog Coins in the Japanese version, are considered to be this game's master currency. Unlike Mythril stones that are more easily earned through play, Gems cannot be earned. They must be bought from the game's home screen or while in an area that would also accept Mythril. Examples include Cid's Lab and Relic Draws. There are six Gem packages that can be bought; in the global release, 100 Gems cost US$0.99 plus applicable tax.