Power, Courage, Wisdom.
HOWEVER, I deeply regretted it and did it in a different order on my Hero Mode run (and intend to do it this way every time I play it from now on). The order that I feel is
objectively the best is
Power, Wisdom, and Courage. It's clear that Power is the easiest to get, so I think it's obvious that they intended something of a
reverse order compared to finding the flames.
To take that a bit further, note that the Sky Keep actually
does have a boss and miniboss. The miniboss is Dreadfuse, and instead of a traditional dungeon boss you have the miniboss gauntlet fought in the Courage-piece room. I think that you were sort of intended to do this last because it's the boss of the dungeon, and even if you weren't, I think fighting the boss gauntlet last is just funner. So although you can often get Courage before Wisdom, I always do Courage last because the miniboss gauntlet is an
awesome finale to the Sky Keep.
Hopefully now you've all seen the error of your ways.
