This script implements the Persona System from the Persona games (specifically Persona 4).
Quoting from the Megami Tensei Wiki:
In this system, you can use Personas to fight enemies. Each character can equip one of those Personas which, as a result, increases all of the user's parameters.
In the original game, the characters have no parameters nor skills and all those depend on the persona they have currently equipped. In this script you can choose the percentages of the parameters contributed by the user and the Persona while, also, use the skills of the currently equipped Persona.
Following the original game's system, Personas can only learn a specific number of skills. When they try to learn a new one, they have to forget an old one (or skip learning it).
Personas can be acquired with two different methods:
By fusing two (or three) Personas to create a new one
During the Shuffle Time
Compared to the original game's fusion system, this script implements a quiet simpler Fusion System, for ease of use. It is divided into a Normal Fusion (two Personas) and a Special Fusion (three Personas). When fusing Personas, the resulting Persona will gain a bonus EXP depending on the Arcana rank (explained later) and the Personas' level used in the Fusion.
Shuffle Time, happens after every battle and if the enemy has dropped any Persona cards. Along with the Persona cards, enemies drop Blank cards and Penalty cards. There are two different Shuffle methods: Rotating cards and Memory match. During the first method, the cards rotate either horizontally, diagonally or a combination of both. During the Memory match, the player has to match two cards together, with a maximum number of attempts. If the player has picked a Blank card during the Shuffle Time, nothing will happen (no Persona will be acquired), but if they pick a Penalty card, they will lose all battle rewards (no EXP or Gold will be acquired).
Additionally, Personas have classes called Arcanas. Quoting (again) the Megami Tensei Wiki:
Each Arcana has its own rank and when it reaches a specific one the Persona of that Arcana can evolve into a stronger one (you can choose which Personas can evolve and at which rank).
You can check all the available Arcanas through the Social Link option in the main menu, along with its rank, its individual Social Links and their description. You can choose, for each Social Link, which actors it is consisted of.
You can change for each user which Personas they can use, if he can use only one, set the maximum rank of each Arcana separately, set whoever you want as a Social Link of an Arcana and change them at any point of the game, call the Shuffle Time whenever you want and with which ever cards you want, use a common event when a Persona is being evolved (if you want and for whichever Persona you want), set the position of a couple of small windows, pick some colors here or there, set the percentage of the parameters individually (for each param, xparam, sparam etc.) and many more that I may have missed. You can check all the possible settings in the script.