Exorcism

Exorcism is a method to forcefully remove demons, Ghosts, and Angels from their Vessel commonly through Latin incantations and prayers.

Pad of Definitions
As the Pad of Definitions (1.04 Phantom Traveler) says, "exorcism is the act of driving out or warding off demons from persons, places or things that are possessed or infested by them, or are liable to become victims or instruments of their malice. During the exorcism ritual, a solemn and authoritative adjuration of the demon is applied in the name of God or any of the higher powers to which the demon is subject."

Usage
In the series, exorcisms are presented as having two parts. The first expels the demon from the occupied vessel (as black smoke) and the second sends the demon back to Hell (shown as the black smoke being sent downward leaving charred marks on the floor). The second part is not mandatory, or can be interrupted, allowing the demon to escape and possess another vessel.

It is clear from what Sam Winchester says in Phantom Traveler and Devil's Trap that the boys skip the Invocation and Psalms and jump directly to the Exorcism proper. It is understandable, given that it is not as though they have all the time in the world, especially in Phantom Traveler.

It is probably the method with the best survival rate for possessed humans, even if some do not make it after the possession is lifted.

Story
Several adaptions are used in the series, all of them being taken from the Rituale Romanum. The following is a direct line-by-line translation of the Psalms for rites of exorcism and the Rituale Romanum, with annotations on differences observed in various episodes.

In Phantom Traveler
As seen in Phantom Traveler, a version of the Psalm 68(67) is recited by Sam Winchester as he read it in his father's journal: "Regna terrae, cantate Deo, psallite Domino (...) per caelum, caelum antiquos, (...), glori Patri", which can be translated to English as: "Kingdoms of Earth, sing to God(...) in the presence of heaven, venerable heaven, (...) praises to the Lord". However, a lot of differences from the Psalm are presented. Others...

"Exorcizamus te, omnis immundus spiritus, omnis satanica potestas, omnis incursio infernalis adversarii, omnis legio, omnis congregatio et secta diabolica. Ergo, omnis legio diabolica, adjuramus te ... cessa decipere humanas creaturas, eisque æternæ perditionìs venenum propinare... Vade, satana, inventor et magister omnis fallaciæ, hostis humanæ salutis... Humiliare sub potenti manu Dei; contremisce et effuge, invocato a nobis sancto et terribili nomine... quem inferi tremunt... Ab insidiis diaboli, libera nos, Domine. Ut Ecclesiam tuam secura tibi facias libertate servire, te rogamus, audi nos. .' "

Translation: "We exorcise you, every impure spirit, every satanic power, every incursion of the infernal adversary, every legion, every congregation and diabolical sect. Therefore, every diabolical legion, we adjure you ... Cease to deceive human creatures and giving them the poison of eternal damnation ... Begone, Satan, inventor and master of all deceit, enemy of man's salvation ... Humble yourself under the mighty hand of God; tremble and flee when we invoke the Holy and Terrible Name which causes hell to tremble ... ... From the snares of the devil, deliver us, O Lord. That Thy Church may serve thee with the making freedom to serve, we beseech Thee, hear us."

In Swap Meat and Repo Man
"Exorcizamus te, Omnis Immundus Spiritus, Omnis Satanica Potestas, Omnis Incursio Infernalis Adversarii, Omnis Congregatio et Secta Diabolica, Ergo Draco Maledicte, Ut Ecclesiam Tuam Secura, Tibi Facias Libertate Servire, Te Rogamus, Audi Nos!"

Translation: "We exorcise you, every unclean spirit, every satanic power, every incursion of the infernal adversary, every congregation and diabolical sect, Dragon, therefore, O cursed one, So that your Church, To Thee in secure liberty, we beseech Thee, hear us!"

Reverse Exorcism
First revealed in What's Up, Tiger Mommy?, this was performed by Sam based only on theory that it would work the opposite as the conventional rite. It proved to be effective when Sam read the verse backwards to 'reverse-exorcise' a demon, trapping it back in its host body and allowing the Winchesters to stab it with Ruby's Knife.

"Et Secta Diabolica, Omnis Congregatio, Omnis Legio, Omnis Incursio Infernalis Adversarii, Omnis Spiritus, Exorcizamus!"

Cure Exorcism
A new type of exorcism pioneered by Max Thompson is introduced in Clip Show that can be used as part of a ritual to cure demons. After the demon is injected with purified blood for several hours on consecrated ground until he starts to turn human, the exorcism is performed with the exorcist's bloody hand over the demon's mouth and the demon turns human again. The chant is much shorter than the original, keeping only the first two lines and replacing the rest with the Latin translation of 'Fix this soul!' and then declaring the soul to be 'Washed!' or 'Cleansed!' twice.

Mental Exorcism
Although any being can perform an Exorcism by reading or reciting the ritual, some beings possess the power to naturally exorcise demons without the need of a ritual. The exact method is unknown, although it largely depends on a being's focus and innate power or control over demons. This is a very rare power.

Characters with this power

 * Famine
 * Jesse Turner
 * Sam Winchester (after consuming sufficient quantities of demon blood)

Tactile Exorcism
Abaddon had the ability to send a demon back to hell merely by touch.

Alternate Ritual Exorcism
Astaroth knew a spell that exorcised a demon. This spell was completely different from the ritual used by hunters. It also didn't affect the demon doing the exorcism. The recited spell is in an unknown language:

Monyé valack forsa, ulu iri regatt ruac, fieesh nieesh forthsa lé inmist infirum forthsa por un betest a té un fornalles ecclaisee

Enochian Exorcism
An enochian chant was used by the townspeople of a church in Blue Earth, Minnesota. It was effective in exorcizing demons. However, this chant, provided by the Whore of Babylon, proved to be fake and meant "you breed with the mouth of a goat". The demons were actually under orders to evacuate their hosts upon recitation of the fake enochian exorcism.

Other
Lilith claimed to have sent Ruby to hell. This feat was done by Lilith very discreetly, without any noticeable noise or visual cue. If Lilith was telling the truth, this unknown method of exorcism was one of, if not the, quickest and most effective exorcism to date. However as Ruby later returned and was secretly working for her, its likely Lilith was simply lying.

Origin
Exorcism from Late Latin exorcismus, (from Greek ἐξορκισμός exorkismos - binding by oath) is the religious practice of evicting demons or other spiritual entities from a person or place which they are believed to have possessed. Depending on the spiritual beliefs of the exorcist, this may be done by causing the entity to swear an oath, performing an elaborate ritual, or simply by commanding it to depart in the name of a higher power. The practice is quite ancient and part of the belief system of many cultures and religions.

Trivia

 * It appears that the Supernatural production team/writers did a cut and paste from bits and pieces of at least one version of the ritual and possibly some other prayer(s).
 * When Sam first performs an exorcism in Phantom Traveler, he reads a Rituale Romanum from John's Journal. However, over time both Sam and Dean memorize the ritual.
 * In Supernatural, exorcisms appear to cause demons great pain, as they have been used as minor torture. They also seem to cause demons great fear, as they have been used as blackmail several times, though it may be the prospect of returning to Hell that scares them.
 * Not all demons appear to be affected by exorcisms: Abaddon, a Knight of Hell proved completely immune to one.
 * At least one exorcism has been performed in every season to date.

Appearances

 * Season One
 * Phantom Traveler  (First appearance)
 * Devil's Trap
 * Season Two
 * Crossroad Blues (Interupted)
 * Born Under a Bad Sign
 * Season Three
 * The Magnificent Seven
 * Sin City (Interupted)
 * Malleus Maleficarum  (Alternate Ritual Exorcism)
 * Jus In Bello
 * Long-Distance Call  (Medieval Exorcism)
 * No Rest for the Wicked (claimed and mentioned only)
 * Season Four
 * Metamorphosis (Mental Exorcism)
 * It's The Great Pumpkin, Sam Winchester  (Mental Exorcism)
 * I Know What You Did Last Summer (Mental Exorcism)
 * Death Takes A Holiday (Mental Exorcism)
 * The Rapture (Mental Exorcism)
 * Season Five
 * I Believe The Children Are Our Future  (Mental Exorcims)
 * Swap Meat
 * My Bloody Valentine  (Mental Exorcism)
 * Season Six
 * Let It Bleed
 * Season Seven
 * Repo Man
 * Season Eight
 * What's Up, Tiger Mommy?  (Reverse Exorcism)
 * A Little Slice of Kevin  (Partial)
 * As Time Goes By (Ineffectual)
 * Clip Show  (Cure Exorcism)
 * Sacrifice (Cure Exorcism)
 * Season Nine
 * Devil May Care (Tactile Exorcism)
 * Blade Runners
 * Mother's Little Helper