I'm interested in how this mini-game works. The reward scheme will be important for the long-term value of these trials (for example, regular min ilv EX Shiva is a fun challenge too but no one is doing it because there's no reward worth the effort).

Was there any more info on this? A "game" implies something you can lose, or at the very least RNG similar to moogle scratchcards. Will we be running Shiva Unreal 500 times to have a "chance" at that 1% Faux Hallows top prize?