Bloody Mary

One of the most famous ghosts of them all: Bloody Mary. 

The tale varies from place to place - even the person who was thought to be the original Mary varies greatly. I began digging into this myth because of my own story and found that if you're writing a paranormal, you could morph this ghost into whatever you need it to be. It can be a good or bad depending on which stories you hear.

Of course we all know the one where you call out and she's supposed to rip your face off or do something equally terrible - but, did you know that Bloody Mary could be referring to the Virgin Mary? In this case, she does not harm you and may offer protection of some sort. Then, there was a legend where you'd stand in front of a mirror holding an apple after brushing your hair 100 times and Bloody Mary would reward you with a peak at your future husband.

Then there are other versions where an animal appears instead of Mary - such as the Donkey Lady or Mary Wolf.

There's many many legends about who she was. "The loony woman next door", a young woman named Mary Worth whose child was killed or murdered and the people thought she was the one who did it (in which case you're supposed to say "I believe Mary Worth" or "I don't believe in Mary Worth" or "I hate Mary Worth" or "Bloody Mary I killed your baby" or "Bloody Mary I have your baby".) the bloody English queen Mary herself, Mary queen of Scots, Mary Magdalene, an ax murderer, a child killer and many more.

Sure, most of stories end badly after you've called to her but in some cases, she can give you toys or candy, sometimes you just get to see what she looks like, you can ask her questions, harmless scratches appear on your skin, or the bathtub water turns red.

If you're writing a story, it can go either way - good or bad - depending on how you want it. I found most of this information at this site: The Face in the Mirror, Looking at Bloody Mary, Mary Worth and Other Variants of a Modern Legend
And also at wikipedia though, the site above gives the most information I could find.

Hope I could help!
Until next time~!