Creepypasta idea - 13

I've been reading a lot of creepypastas lately (I'm kind of addicted to them. They're like my guilty pleasure x)) I've been reading them so much in fact that I've been able to find inspiration for many ideas just based on just about anything, even the most simplest, mundane things. My latest idea I've decided to post here because it's one that I think could potentially be a really good creepypasta, and I really like the idea so far, more so than most of my other ideas that I've thought of (and forgotten for the most part). The fact that I haven't forgotten it already is a good sign xP.

In my abnormal psych class, we were learning about dissociative (for some reason Firefox doesn't seem to think this is a word) disorders. One of them, dissociative identity disorder (DID) a.k.a. multi-personality disorder, has become the inspiration for my latest idea, which I've decided to title 13. If you know nothing or very little about DID, I recommend reading this article which explains it pretty well in easy to understand terms.

The basis of the story is that a young woman who suffers from DID and has 13 distinct personalities. They are all mutually cognizant (they are each aware of the other personalities). As with all of those who have DID, each of her personalities is different-have different names, different genders, different ages, etc; each is essentially a different person. So that means that along with the main character or "host", I'll be having to think of 13 other distinct characters for each personality.

There is one personality I have fleshed out some, "number 13" I've come to call him (and I may just refer to the other personalities as numbers, too). What I see in my mind when I picture him and the others, I see the 12 other personalities lined up, holding hands with the main personality in the middle. Off to the side in his own little space is a shadowy figure-"Number 13". I haven't figured out exactly what his or its (13 doesn't have any real distinct features) role, but I had the idea that he wants to terrorize and perhaps take over the main personality entirely and the other 12 personalities try to protect her. Sometimes she does switch over to this dark personality, though not because she intended to and it tends to manifest itself as a psychopathic individual.

Due to past circumstances involving 13, the young woman finds herself in a mental institution and this is where the story starts. I plan on having the story take place in the hospital, outside of the young woman's mind where she and her other personalities interact with psychiatrists, etc., inside of her mind where she and her personalities interact with one another with the exception of 13 who is never seen by the other personalities except by one, a little girl who sometimes sees him "spying" on them, and the young woman's past in the form of flashbacks.

Other than that, I haven't really thought of any ideas for the story. I do plan on watching movies/reading books about people with DID so I can get a better idea of how it works and hopefully gain some inspiration for the story. What do you think? Do you have any ideas/suggestions?

This actually sounds awesome on a lot of levels. One thing I've done with that kind of idea is having two people in one body, like Renn in RK, but never that many at once. It seems a novel idea, and something that may just work for a deep, psychological thriller-type story.

So M. Night Shyamalan kinda stole my idea :/

https://www.youtube.com/watch?v=84TouqfIsiI