[quote=WinterNightSky]
Well the only thing I need more information about right now is the Persona/Arcana/Shadow.
[/quote]

From what I can decipher (if we're basing this roleplay on Persona 4), Personas are a part of someone's personality, which manifests itself into a physical form, with thoughts and abilities of its own, while still being under the control of the actual person wielding it (because they are still of the same mind). They usually take the form of demons, mythological/folklore figures, gods, and goddesses.

EDIT: [url=http://megamitensei.wikia.com/wiki/Persona_%28Concept%29]I found a wiki-page that explains Personas better[/url]

Arcana is the "class" of a Persona, so to speak. Personas of different Arcana have different abilities and specializations, as well as weaknesses. Arcana is based off of Tarot Cards. The Arcana of a Persona is usually a representation of one of the most notable features of someone's personality. For a more in-depth explanation of the Arcanas,[url=http://megamitensei.wikia.com/wiki/Arcana] Here's a list of them[/url].

Shadows, are explained in the OP. In Persona 4, Shadows are versions of people that manifest in the alternate dimension where the Personas can be used (In Persona 4's case, it was the "Midnight Channel"). In Persona 4, Shadows were "repressed" parts of people's personality: a part of them which they never wanted anyone to see. However, they were always twisted and perverted versions of that repressed portion. They got stronger and stronger the more the person whose Shadow it was, denies them (denying the fact that it is truly a part of them). They can only be stopped once that person accepts that the Shadow is indeed a part of them, and once they do, their Shadow transforms into their Persona, and becomes a permanent part of them.

That's where the famous Persona phrase: [b][i]"I am thou... Thou art I..."[/b][/i] comes from (as they usually state that when revealing themselves to the Persona-wielder).

In this setting however, it looks like the OP has his own version of Shadows for the roleplay =)

But all of this is just based on my own understanding, and I don't doubt that a better Persona fan will correct me XD. Though, I hope you can understand the terms better now.