The "Realm" is Freeform. Meaning, any type of character and system can be used in the game.
For example, Dungeons and Dragons, World of Darkness, DBZ, ect are all types of Standard Games which are part of the Role-Playing world.
Also, if a person creates a new race, a new item and so on, it is just as worthy and usable as a prebuilt system. The point of Role-Playing is to have fun, be creative, thus there should be no limitations placed on how or what a character can or may be created from.
Having a Free-Form world can and will cause problems. Since there is no limitation on character’s abilities, if they play a god or demi-god, ect. The responsibility comes to each player on how they do make their characters and do not. If a person does not like another person’s character, then simply do not RP with that person.