Mythic tiers, and Mythic heroes, are generally permitted. This represents the incredible power and potential to be found in the “Outsiders,” above the common folk of the realm.
Rising in tiers within a Mythic Path requires an epic or heroic moment on the part of the adventurer. This often involves thinking outside the box, self-sacrifice and appropriate role-playing. What exactly warrants advancement in a Mythic tier is up to the GM’s discretion.