Quote Originally Posted by Volarmis View Post
Look through the exchange store, as there are some goodies there.
The twelth is generally unusable, because as far as I know the currency is only aquired through promotions (at least I've never had any of it, even after clearing all the maps).
I got a bunch of them starting out and more from the quest dungeon stages. At one point I had over 20, but I stupidly used 10 them in the gacha.