I have to say -- having played all of the Kemco ios rpgs -- this ranks as one of my favorites. Decent story that doesn't take itself too seriously, well differentiated characters, good challenge level, a good set of skills that leads to strategy in battles (versus just auto fighting).
I also got all four endings on hard. In my opinion, in the first play through the best area to get xp is a long thin region just south of the shrine of radiance accessible only via airship. With 5 xp orbs, the chant and the xp booster consumable you can get over 2 million xp in a battle, with the average around 1.5m. Even at level 100+ this translates to 1-2 level ups per battle.
Has anyone gotten the reward from the challenge battle? I have gotten just over 30 million points and still no reward. My strategy involved two characters feeding burst cakes to the other two, who repeatedly fired off their burst chain for 3-4 million damage. Even so, getting over 30 million required repeated attempts and some luck
And a final tip: •••Spoiler: The first four times you beat the final secret arena boss, you get the four ultimate weapons -- 3 of these are well worth the effort (I prefer +int items on the priestess). Each time after that you get a set of 30 stat orbs