How to write a halo novel and get permission to publish it?

To write a Halo novel, start by familiarizing yourself with the established lore, characters, and themes of the franchise. Create an original story that fits within the Halo universe while respecting the existing narrative. To obtain permission to publish, reach out to the rights holder, currently 343 Industries, with a well-prepared proposal outlining your story, how it fits into the Halo universe, and why it would appeal to fans. Be prepared for the possibility of rejection, as fan fiction based on established franchises often has strict legal limitations.