I doubt it's a whole month either. At least not for just the backstory.
Now, if "backstory" here means literally everything about a character that isn't actually drawing their portrait (Like actual backstory, naming sense, species, appearance, personality, if and how that species fit in the story or in the world as a whole, spell card names and themes, patterns, abilities, possible connections to the other new characters and the rest of the cast, what they can do in future appearances, what their boss theme should sound like, what their introduction implies in general, researching mythologic stuff about them, etc), then i could believe that it can take a while.