Allegory Idea

I am wanting to write an allegory that I felt just needs to be written.  I see the story in the scriptures, it just hasn't been told into the story I see.  It is about a lot of spiritual things, like spiritual food, how people starve themselves of the Bible and only "eat" of the Word every Sunday, and even then they sometimes pick at their "food" and don't eat what's been prepared for them.  That's what the allegory was supposed to be about(and it's also what was taught me on a Sunday earlier this year).  But then I got interested in the backstory and the world around the backstory and the characters and so on.  It takes place in a big big city called Wuldon(pronounced like Wool den) that looks like nineteenth century London, except it is always dark there.  And far away beyond the guarded walls and the black forest is the white Kingdom(unnamed) where the good King lives.
Now there's a messenger boy who ran away to find the King in the castle and became his doorkeeper.  A girl whose mother died runs away to find the castle and seeks refuge, and meets the King and eats at his table.  But then she has to go back to Wuldon, and things happen there.  Words are important.