A Rank in Purify are referred to as "Tiers." Tiers are used to power scale exorcist and phantoms from Tier 1 up to Legendary Tier with Mythical Tier being an expectation.
Ranks are assigned mainly by the nation's council, besides mythical tier, in which the exorcist or phantom resides. The councils will review the skill level and information on said exorcist or phantom and assign them anywhere from tier 1 to legendary tier.
Ranks
Tier 1
Tier 2
Tier 3
Pseudo-Legendary Tier
Legendary Tier
Mythical Tier
Tier 1 -> Tier 2: The promotion from tier 1 to tier 2 is fairly simple. All that needs to be done is gain more experience as a general manipulator of kinetic energy. Nearly any Tier 3 can promote a tier 1 to tier 2.
Tier 2 -> Tier 3: A tier 2 exorcist must be recommended to the rank by at least a pseudo-legendary exorcist and the tier 2 must know the first kinetic release "overcharge."
Tier 3 -> Pseudo-Legendary: Must be recommended by a legendary tier and approved by that exorcist's nation council. Upon being approved, the tier 3 must complete a mission and when it's completed, the tier 3 will be promoted to pseudo-legendary.
Pseudo-Legendary -> Legendary: The pseudo-legendary's nation council must deem you worthy of being classed as a full legendary tier exorcist.
Mythical Tier: All nation councils must unanimously agree you're worthy to be classed as a mythical tier.
Tier 1
Tier 2
Tier 3
Pseudo-Legendary Tier
Legendary Tier
Mythical Tier