This "special capability" is a rare ability of Persona, called the "Wild Card. " Personas are the masks that people form in order to protect their hearts from various hardships. Usually each Persona user commands a Persona that mirrors the user's will and may resemble a god or demon. The "Wild Card" is a Persona user that can wield multiple Personas, and can switch between them as if switching between masks, and whose ability increases as their heart grows.

from Chapter 1 of P3P Velvet Blue