Well, let's get into business
Fos is one of the hardest ones to complete, since it requires you to survive 3 days in the Dark Realm, a shadowy place filled with dangers
Meteórisi is one of the easiest, as it requires you to meditate on a mountain, for 3 days
Only after completing the challenges, you'll be offered to be trained, or you can learn by yourself
But there are few temples they can visit
-Simple Temple - Godlike/Superior Beings/Royal
-Iron Temple - Godlike/Superior Beings/Royal
-Complex Temple - Godlike/Superior/Royal
-Emerald Temple - Godlike/Superior Beings
-Extreme Temple - Godlike/Superior Beings
-Chaos Temple - Godlike/Superior Beings
-Obsidian Temple - Godlike
-Diamond Temple - Godlike
-Ultima Temple - Godlike
-Gamma Temple - Gods
-Beta Temple - Gods
-Alpha Temple - Gods
-Omega Temple - Ultimate Gods
But through serious training and upgrades, if they are determined enough, they can go from Royals, to Superior Beings, and to Godlike, to Gods, to Ultimate Gods