The infamous Bloody Mary is a terrifying and disturbing folklore legend involving a ghostly lady attacking you if you say her name three times. She also sometimes reveals your future to you as well. Sometimes she is harmless and other times she is twisted and down right menacing.
Historically, the ritual encouraged young women to walk up a flight of stairs backwards while holding a candle and a hand mirror, in a darkened house. As they gazed into the mirror, they were supposed to be able to catch a view of their future husband's face. There was, however, a chance that they would see a skull (or the face of the Grim Reaper) instead, indicating that they were destined to die before they would have the chance to marry.
In the ritual of today, Bloody Mary allegedly appears to individuals or groups who ritualistically invoke her name, usually by repeatedly chanting her name in a mirror placed in a room that is usually lit by a candle. The Bloody Mary apparition allegedly appears as a corpse, a witch or ghost; can be friendly or evil; and is sometimes "seen" covered in blood. The lore surrounding the ritual (if she is summoned properly) states that participants may endure the apparition screaming at them, cursing them, strangling them, stealing their soul, drinking their blood, or scratching their eyes out.
A modern addition of taunting Bloody Mary regarding her baby indicates the legendary figure's tenuous connection to Queen Mary I, also known as "Bloody Mary", whose life was marked by a number of miscarriages or false pregnancies.