"Mutation is a type of Persona growth that happens sometimes after Fusion Spells. The better the compatibility, the likelier they are. How the Persona grows depends on its rank. The higher its rank at the time of mutation, the likelier a rare or useful mutation is. Some can become a different Persona entirely by selecting "Mutation" in the Velvet Room. A few Personas can only be obtained this way."
Mutation is a gameplay mechanic in the Persona 2 duology. It differs from Evolution in that the Persona does not necessarily change forms, rather the Persona gains power or a new skill, although it is also possible for a Mutation to allow the Persona to evolve.
When activating a mutation, four possible changes can occur:
|Mutation (IS)||Mutation (EP)||Rank||Effect|
|Increased Stats||Parameters increased||Any||Persona's stats increase.|
Can occur repeatedly until the Persona's stats reach maximum.
|Two Ranks up||1-6||Persona's Rank increases by 2.|
|Skill learned||6+||Persona learns its hidden "Mutation" skill.|
|Persona can Change Forms||Modification ability learned||6+||Persona can Evolve into a new Persona, usually a Persona of the Minor Arcana, however a few can "Rank Up", evolving to a higher-level persona of the same Major Arcana. Persona must be taken to the Velvet Room to change forms and returns to Rank 1. "Rank up" mutations can occur if the result is no more than 10 levels above the protagonist, however Minor Arcana mutations do not have this limit.|
In the PSP remake of Innocent Sin, if the player misses obtaining the Prime Personas through the correct story choices, the Initial Personas can be evolved into their Prime forms any time after the story event where they would normally be obtained. In Eternal Punishment, Maia Custom can only be obtained by evolving Maia this way.
Eternal Punishment adds an additional mutation that can occur:
|Unknown ability awakened||Persona gains its Unknown Power, an ability similar in concept to "desperation attacks" - powerful abilities that activate at random, and can only activate if the user is at critical health. There are 6 different types of Unknown Powers; each Persona has one specific type of Unknown Power associated with it.|
The chance of getting a mutation depends on the characters' affinity for the persona, the number of people participating in the Fusion spell, and the type of fusion skill used:
|Compatability||Avg # of uses required to mutate|
|2-Person (Phys)||2-Person (Magic)||3-Person (Magic)|
In Innocent Sin, there is no way to increase the mutation rate, however Eternal Punishment adds the "Mutation Gear" accessory and a Sumaru Genie fortune to increase the chances of mutations occurring.