Players can pay a fee in Gil to open one of 32 chests, keeping whatever is inside when visiting the Gold Saucer. Players can choose to open an item chest, or a Relic chest.
There's even some special one-time-only prizes in there, too. =)
EDIT: I'll probably end up replacing the background with something more fitting later on. Also, there are no repeat chests. Each one contains a different item or Relic.