Monsters in Horror Films (Drafting and Planning)

After researching different Horror 'Monsters' I need to consider which one would suit best. As I said previously I want to base the 'Monster' on the girl from The Ring/Paranormal Activity so the one that would apply to me would be...

The Internal Monster 

Both 'Katie' and the girl from the ring come under this category. 

Katie is completely normal at the beginning of the trailer but as the trailer progresses her internal monster starts showing and the audience are intrigued as to why she has turned, when it was in fact the 'external' monster that was to be feared. 

Similarly in The Ring when the girls crawls out of the television her Internal Monster is shown straightaway and she is not a ordinary little girl, but like Katie she is to be feared, and becomes the threat in the film.