Hello,
The Sims Supernatural's creatures are taken from popular folk stories, as far as I know. There are vampires, werevolves, fairies, ghosts, zombies etc. which have been around before The Sims and will be around years after The Sims' disappearance, should there be one.
I am pretty sure that you may write about the creatures.
Happy writing! While you're at it, check out NaNoWriMo.
