When I made a Organization XIII cloak, I used a Simplicity pattern #5840 ( http://www.simplicity.com/dv1_v4.cfm?design=5840
) it is a jedi pattern, but I think it worked well.
The only thing that I really did differntly was to round off the back side of the hood, you do not want a pointy hood. You may also want to make the hood bigger so that it will fall over part of your face, the best way to so this is to make it taller, but don't change the size of the neck it will make it harder to attach to the rest of the garment.
You will also need to add a zipper up the front, the pattern only calls for a closure at the neck.
I also added horsehair braid to the bottom so that it would look a little stiffer around the bottom.
Other than that I think is was just the one from the pattern, the only other thing that I will say about this pattern was that if you are very tall I would recomend that you add lenght to the sleeves and bottom, I have trouble with most of the patterns being to short.
Message me if you have any questions.