Medium

A medium is a person who is mystically attuned to the afterlife. They have the psychic ability to commune with the spirits of the dead, and often use their own bodies as host vessels through which these spirits may communicate with the living. Mediums may also possess other psychic abilities such as being able to perceive future portents or recognizing the spiritual and/or emotional state of another individual, which comes in handy if said individual happens to be possessed.

On True Blood, a witch named Marnie Stonebrook could tap her mystical reserves to commune with the dead. By invoking this power, she opened a door that allowed the spirit of a powerful witch named Antonia Gavilán de Logroño to take possession of her.

On Penny Dreadful, a woman named Evelyn Poole, aka Madam Kali, was hired to conduct a séance at the home of Ferdinand Lyle in 1891 as part of a party. Kali failed in invoking the presence of any spirits, but one of the party guests, Vanessa Ives, stole the show when the demon that had been possessing her made quite a spectacle of itself.

Television

 * Penny Dreadful: Seance
 * True Blood: She's Not There