You lived in the slender mansion with the creepypasta, why did you live there? You are a bio-human, created by scientist and become a human weapon also becoming a cannibal at some point when escaping, then becoming Slenderman's first female proxy. In your story being created by scientists, of course, it wasn't much of a problem for you since you had become immortal. Even though you were created you grew like a regular child until at the age of 17 times stopped for you once you now being over a few centuries old. It turns out that the scientist stopped your aging during an experiment, you wondered only meeting Slenderman and becoming his proxy. Now here you are living with murders like you with backstories about their history which the internet can bestow mortals entitled 'Urban Legends' or 'Fiction'.