A ghost is the disembodied spirit of a once-living wizard or witch. Only magical beings can become ghosts. Many ghosts take up residence within Hogwarts Castle. These fleshless spirits were either afraid of death or have some extraordinarily strong connection to the locations they haunt.
- Sir Nicholas: "Not everyone can come back as a ghost."
- Harry: "What d'you mean?"
- Sir Nicholas: "...Wizards can leave an imprint of themselves upon the earth, to walk palely where their living selves once trod... But very few wizards choose that path."
- — Sir Nicholas and Harry Potter discussing ghosts.[src]
In their paranormal state, ghosts are unable to have much physical influence. They are visible, and appear as a greyish-silver apparition of their former (living) selves. They pass through solid objects without damaging themselves or the material, but create disturbances in water, fire and air. The temperature drops in the immediate vicinity of a ghost. Their appearance can also turn flames blue.
In passing through an object, they may impart a sensation of icy coldness. However, they are apparently moved by gusts of wind, as demonstrated when a petrified Nearly Headless Nick was wafted to the Hospital Wing by a large fan, although this may have been possible due to his petrified state. Ghosts are either capable of, or pretend to be capable of, almost being able to taste rotten food.
Ghosts also appear to celebrate their deathday, as Nearly Headless Nick did so on October 31st in 1992. They tend to be very sensitive concerning the circumstances of their death, often showing great hesitancy when asked by others how they died.
They are also weightless and may fly in any direction. Ghosts cannot be destroyed, however, they may be petrified with the gaze of a Basilisk. This can be reversed by a Mandrake Restorative Draught, although the method of administration is unclear. Ghosts may also be repelled by magical light, and therefore will retreat from a Wand-Lighting Charm. Ghosts can also be frightened and retreat from a Skurge Charm, which will also clean up any ectoplasm that they have precipitated.
In 1996, after Sirius Black's death, Harry had a conversation with Nearly Headless Nick in which he asked if Sirius could come back as a ghost like others and Nick himself. Sir Nicholas explained that only wizards who fear death are likely to become ghosts.
As ghosts are imprints of souls of the said deceased wizards and witches, they are unable to move beyond the veil, and are forever trapped in the world of living as intangible beings. Due to this, few would choose this path. Depending on the conditions of the person's soul, they may not be able to return, as Tom Riddle's self-mutilated soul is trapped in limbo for eternity and cannot become a ghost.
The Ministry of Magic seems to have at least a degree of power and jurisdiction over ghosts, as Moaning Myrtle was forced to return to her place of death, which was Hogwarts School of Witchcraft and Wizardry, when she disrupted the wedding of the brother of Olive Hornby. The Spirit Division is the division of the Department for Regulation and Control of Magical Creatures deals with ghost welfare.
Each House at Hogwarts has a patron ghost. Each of these ghosts once belonged to their corresponding House. They apparently serve as a representative to their House, as well as serving the role of messenger or guide to those who are still unfamiliar with the House they were sorted into. It is unknown for how long they may retain this title.
- "I know nothing of the secrets of death, Harry, for I chose my feeble imitation of life instead..."
- —Sir Nicholas
The Gryffindor house ghost is Nearly Headless Nick. He is known as a friendly ghost who was nearly beheaded, but the job was poorly executed, which was how he obtained the nickname of "Nearly Headless Nick". He prefers to be addressed as "Sir Nicholas". His real name is Sir Nicholas De Mimsy-Porpington.
The Ravenclaw house ghost is the Grey Lady, also known as Helena Ravenclaw. She was the daughter of Rowena Ravenclaw, making her the only house ghost to be directly related to one of the four Hogwarts founders. She is renowned for being instrumental in assisting Harry Potter in the search for the Horcruxes.
The Slytherin house ghost is the Bloody Baron. He is well known for being extremely unsocial and many students, including those of his own House, are known to be slightly afraid of him. The Baron is also the only one known to be able to control Peeves. The Bloody Baron is responsible for the death of Helena Ravenclaw as well.
- Bloody Baron
- Professor Cuthbert Binns
- Fat Friar
- Helena Ravenclaw (a.k.a. the Grey Lady)
- Myrtle Warren
- Lord Draben
- Sir Nicholas de Mimsy Porpington
- Sir Patrick Delaney-Podmore
- Edgar Clogg
- Wailing Widow
- Ghost at Gryffindor Tower
- Knight with an arrow sticking out of his forehead
- Ragged man wearing chains
- Portly ghost
- Ghost of a highwayman
- Unidentified ghost (VII)
- Gloomy nuns
- Unidentified ghost horse (I)
- Unidentified ghost horse (II)
J. K. Rowling used the term 'Ghost Plots' for the stories that never mentioned or yet published in any books. JKR indicated that Ghost Plots tended to be "superfluous to requirements" "had to be sacrificed for the bigger story". Thus, Ghost Plots tended to be more peripheral or tangential to the story making them a hinderance to a tighter more focused plot. Sometimes JKR originally had two characters playing the same role making one of them redundant.
Some Ghost Plots were removed quite early in writing process, while others were removed later (as indicated when JKR accidentally gave details of ghost plots in answer to fan questions). It is possible that some of what appear to be red herrings were remnants of ghost plots removed further along the writing process.
Known Ghost plots include:
- Dean Thomas's father. JKR originally planned for Dean Thomas to find out about his biological father being a wizard, why he left and why he was killed. In DH, Dean mentions that his biological father left when he was young and that he does not know whether his father was a muggle or a wizard. JKR said that she sacrificed Dean's backstory for Neville's - though what we know of Neville's backstory seems to have been known by Neville all along.
- Arthur Weasley's death. The family dynamics would have been different and actions and words attributed to Arthur in later books would have to have been said or done by someone else (or omitted altogether) if JKR had gone ahead with her original plan to kill Arthur off.
- Pyrites. His role in the Potters' betrayal / deaths was likely filled by other characters with more of a role in the story.
- Mafalda the Weasley cousin. Mafalda was very intelligent with the sort of belligerance which seemed endemic in Slytherin (ie Draco, Pansy). JKR said she was dropped because Rita Skeeter did a better job of providing necessary information and having both characters was redundant.
- Florean Fortescue. JKR admits that Florean's presence in POA was originally meant to set up a subplot where Harry later turns to Florean for information in DH. However, JKR subsequently decided to use Phineas Nigellus Black and Helena Ravenclaw instead to pass on this information .
- Garrick Ollivander being the product of a wizarding father and muggle-born mother. Garrick's parentage is hinted at when he knows all about the elder wand and wandlore but nothing about the Tale of the Three brothers and other fairytales unfamiliar to muggles and muggle-borns.
- Hermione Granger's sister. JKR never had occassion to introduce her.
Behind the scenes
- In the video game Harry Potter: Quidditch World Cup, a ghost named Edgar Clogg haunts the Quidditch pitch and provides coaching.
- Professor Amberose Swott may have become a ghost after death.
- According to W.O.M.B.A.T., ghosts may have the ability to move liquid or gas.
- The ghosts Edmund Grubb, the Black Knight and The Toad were cut from final drafts.
- It is possible that while ghosts might be silver-greyish to the living, it is possible that through their eyes, they see themselves and each other the way they looked alive, as Nearly Headless Nick was able to read a Ghost letter that appeared to be transparent to Harry, meaning that he could not see any written text on it, even if Sir Nicholas could.
- Although Killing rips the soul, true remorse can heal it again. One example would be the case of The Bloody Baron as he killed Helena Ravenclaw, but felt remorse over her death, thus he was able to come back as a ghost.
- The house ghosts are known to have died in different time periods. The Grey Lady and the Bloody Baron both died shortly after the founding of Hogwarts. Sir Nicholas died in 1492. It's unknown when the Friar died. Thus, it's not known at which point in Hogwarts history the house ghost position was created or if other ghosts ever held this title.
- On Pottermore, there is a feature called "The 6 best-loved ghosts at Hogwarts."
- Harry Potter and the Philosopher's Stone (First appearance)
- Harry Potter and the Philosopher's Stone (film)
- Harry Potter and the Philosopher's Stone (video game)
- Harry Potter and the Chamber of Secrets
- Harry Potter and the Chamber of Secrets (film)
- Harry Potter and the Chamber of Secrets (video game)
- Harry Potter and the Prisoner of Azkaban
- Harry Potter and the Prisoner of Azkaban (film)
- Harry Potter and the Goblet of Fire
- Harry Potter and the Goblet of Fire (film)
- Harry Potter and the Order of the Phoenix
- Harry Potter and the Order of the Phoenix (video game)
- Harry Potter and the Half-Blood Prince
- Harry Potter and the Half-Blood Prince (video game)
- Harry Potter and the Deathly Hallows
- Harry Potter and the Deathly Hallows: Part 2
- LEGO Harry Potter: Years 1-4
- LEGO Harry Potter: Years 5-7
- Harry Potter: Quidditch World Cup