Persona 4 is one of, if not the most epic game of all time. It was a PS2 game that was amazing, so amazing in fact that they made an anime version of the game (called Persona 4 the animation, is 26 episodes long, I highly recomend it) and then rereleased on the PSvita with loads more stuff.
Anyhow, to try to explain without giving away any plot points, in Persona 4 you have the Fool arcana, and the ability to summon monsters known as Persona's. Since you are special you can summon more than one Persona. The way you do this is by getting to know other people and befriending them, all of the people having diffrent arcana assigned to them. The more you know some people the stronger your personas you can get of that arcana is (for example, say that you have befriended the person of the justice arcana up to level 6 of 10 and the person of hanged man up level 3 of ten your justicew Personas will be stronger than your hanged man Personas)
Great game, I highly recomend it, or the show if you'd rather prefer that