You outta hear this now. A Demon Hunter is something called a Prestiege Class.
But Tarne, what is a prestiege class?? HALP!: Do not fear. A prestiege class is a special class not playable at character creation, with the acception of Draenei Vindicators, and Troll Witch Doctors (if there are more please add that in here). 9 times out 10 ten a prestiege class is extreamly hard to obtain ICly, and therefor you must put in a lot of work ICly and OOCly to obtain it.
How do I obtain a prestiege class?: For starters, you must be a grunt. After you become a grunt you must choose a prestiege class and fill out a prestiege class application. After you fill out the application you must send it to one of the GMs. They will talk about with the others, and if your application is accepted, they will let you know and you may begin your "training".
How does one train?: To train a prestiege class you must do either of the following.
Option one. You could find someone who already has that prestiege class and convince them to train you to become that class.
Option two, you can make your own NPC trainer (or however it is done for that class) and write out the story on the fourms, which must get approved with each post as you go along. I am unsure if you need to do story posts if you have a trainer as a player...someone clarify?
Can I become anything?: Not -exactly-. There is a list of available prestiege classes listed on the CotH wiki, feel free to take a gander at that if you so wish.
I know I left out a few things, but that is the basic gist of how the prestiege class system works.
Oh and also, GMs can easily give players a spell like metamorphisis

It is a simple command really, all you need is the spell ID.
And yes, you must create a game account, but make sure it is the same log in info as your fourm.