I am an egg that contains a palace, or rather, I am a palace that has been contained in an egg.
In any case, I am an underworld marvel made into a miniature so that I can travel between worlds.
He who has the magic to turn me back into a palace will be able to enter it in the upper world, and take from me what he needs to serve my mistress.
That is all I can say. To say anything more would be to give my secrets away!