What kind of supernatural elements are used in gothic literature?

Gothic literature delves deeply into mysticism, monstrosity, and hauntings. The literary canon for this genre contains a rather staggering array of what can be identified as "supernatural" phenomena. Below are just a few.
Ghosts and hauntings. Typically in settings of large, cavernous, austere castles and estates, the characters of Gothic literature are assailed by ghosts and hauntings of many kinds. Jane Eyre is haunted by her dead uncle's spirit in the "red room" of her aunt's home. The children of Henry James's "Turn of the Screw" are plagued by the ghosts of two former staff members, with deadly outcomes. 
Monsters. Mary Shelley's Frankenstein revolves around an unnaturally animated (and yet curiously human) monster who is grotesque in appearance. Bram Stoker's Dracula, and its original inspiration Carmilla by Sheridan Le Fanu, feature narratives pushed and pulled by the drama surrounding vampires. In The Strange Case of Dr. Jekyll and Mr. Hyde, Jekyll possesses a violent alter ego, Hyde, which can only be kept at bay by a serum.
Inexplicable happenings. Other works of Gothic literature still employ supernatural elements; they simply do not fall into such explicit categories as "ghost" or "monster." For example, in Oscar Wilde's The Picture of Dorian Gray, Dorian Gray's soul and behavior become supernaturally intertwined with a painting of him. The painting mysteriously changes as the character commits more vain and terrible actions in real life. The painting grows older, uglier, and more unseemly, yet the character never seems to age.
These supernatural elements are, in many ways, literary sketches of "evil" human behaviors and impulses. The origins of these ghosts, monsters, and strange happenings are essentially projections of cruelty, vanity, mental illness, and unresolved past trauma. Even more examples of the supernatural as a literary element in Gothic works exist beyond those mentioned here.