Fire in some works has the ability to burn away imperfections and evil. It burns up evil or evil-associated creatures, such as demons and the undead, entirely, and it works more effectively against those beings than most weapons or attacks would. It can also sometimes burn away only the evil parts, leaving any pure or good parts unharmed. In such cases, it is useful for de-possessing hapless creatures who have been possessed by evil beings.
This ability draws on fire's association with life and its ability to burn impurities out of metal as well as the ability of hot objects to kill bacteria and decompose poisons; combining these ideas to create a force against evil. This will often be a form of magic fire, but sometimes all fire will have this property.
In some settings, the characters will believe that fire has this property, and act accordingly, even though fire does not actually have any extra powers against evil.
This may be a reason why Fire Keeps It Dead, the trope for where burning a body prevents it from coming back to life. Supertrope to Burn the Undead, which is where the purifying powers of fire cause the undead to be vulnerable to destruction by fire. Compare Heal It with Fire. Often associated with Sacred Flames. If the purification has to do with the magical properties of the fire, then it's an example of Magic Fire.
- Blue Exorcist shows this with Rin and his flames. It's particularly noticeable in the Kyoto Saga, when his flames engulf the entire mountain and everyone on it. Many of his fellow students flinch away, expecting to be hurt by them as they have in the past, as Satan's flames are deadly, but no one is harmed and all the demonic rot is cleared away.
- Moriarty the Patriot combines this with Evil Is Burning Hot: William is strongly associated with fire, which, since he's the Villain Protagonist, shoudl be evil—but it's also shown to be cleansing the world of the rot and evil he sees in it, and purifying people's souls.
- Child of the Storm has this as a common technique for dealing with the undead, and with dark magic. Phoenix fire in particular is cited as being very good at purifying... though if you're not careful, it'll 'purify' everything it touches into oblivion, and it can be corrupted, resulting in the Dark Phoenix.
- In Children of an Elder God, Asuka is a pyrokinetic. She wants her fire to become a tool to purify instead of a weapon to destroy.
The flames of hell are the fires which burn away impurities.
- Daybreakers: Sunlight would usually Burn the Undead, but among human fugitives is man who was once a vampire and was restored to humanity by firey exposure to the sun. This gives Dalton hope that he and the rest of the world could be cured of vampirism. It works — Dalton experimentally re-creates the event and restores his humanity.
- Enjo: Goichi the devout Buddhist comes to Shukaku Temple to become a monk. He finds that the monks there really don't give a rat's behind about Buddhism and are running the temple as a tourist attraction, bringing in crowds of crass American soldiers. And for that matter, the abbot of Shukaku carousels in the local Red Light District and has impregnated a geisha. So Goichi burns the temple to the ground.
- In silent western Hell's Hinges, the bad guys burn down the church. The enraged hero then sets fire to the dance hall that doubles as bad guy headquarters. The ensuing conflagration burns down the whole wicked town.
- A Nightmare on Elm Street Part 2: Freddy's Revenge: Freddy eventually possesses Jesse and goes on a murderous rampage. Lisa decides to confront Freddy and beats him with The Power of Love, which sets him on fire. Then Jesse crawls out of Freddy's torched remains alive and well.
- Fire is pretty much the surefire way of dealing with The thing (from The Thing (1982) and The Thing (2011)), being a biological horror that needs to have every cell destroyed so it doesn't come back.
- In Chronicles of the Kencyrath fire is one of the few reliable ways to kill corrupted beings like Haunts and Changers, and usually the most practical. Also, until the body of a Kendar or Highborn is burned, their spirit is bound to the world.
- Daughters of the Moon has a rare Pure Is Not Good version with the Cold Fire, a ritual by which high-ranking Followers burn away their mortality and bind themselves to the Atrox as its ageless servants.
- In the Discworld novel Carpe Jugulum, the flames of the Phoenix only burn evil creatures. Granny uses it to keep the darkness of the vampires at bay.
- Just before the summit of Mount Purgatory in The Divine Comedy, there is a massive wall of fire all humanity must pass through to purify their lust. Unlike every other penance of Purgatory, Dante actually must go through the wall of fire in order to enter Heaven. Not eager to burn away parts of his soul, Dante hesitates until Virgil reminds him Beatrice is on the other side of the fire. Dante jumps in.
- In The Dresden Files, Harry notes that fire really is a highly-effective weapon against all sorts of nasties, as well as being used against magical enchantments. Fire can disrupt and destroy enchantments when used with that intent, and any wizard worth their salt in combat learns how to use fire first.
- Harry Potter and the Deathly Hallows, Fiendfyre turns out to be one of the few ways to destroy Horcruxes.
- Invoked by name by Firesong in the last Mage Winds novel, as he finally destroys Ma'ar's soul by incinerating its refuge in the Void.
- Subverted in "Literature/The Road Virus Goes North," a short story by Stephen King. A horror writer buys the last surviving painting of a troubled artist who burned all his other works and then committed suicide. When he realises the painting is cursed he tries to get rid of it, but the painting keeps returning intact. Eventually he burns the picture, because that's what works in the books, right? Unfortunately it turns out that the artist didn't burn all his paintings except this one, he burned all his paintings including this one.
- Referred to in the title of the George MacDonald novel Salted By Fire ("salted" meaning purified in his Scots dialect). The plot involves a clergyman who doesn't really believe going through trials that "burn away" his apathy and self-centeredness, allowing him to truly find faith.
- The supernatural elements of Shakugan no Shana are heavily fire-themed, which extends to its Hunters of Monsters being referred to as "Flame Hazes" and generally having at least some ability to manipulate fire as an attack. Back when she lived on the road Shana followed a more utilitarian version of this, using her flames to burn away dirt and disease as a substitute for bathing.
- In Sunrise, many of the flenser gangs have degenerated even further than they have in previous books. Three of the last surviving members of one particular gang are found in an abandoned JC Penny in a filthy den full of rotting human remains. At least one or two are afflicted with debilitating illnesses, and the one flenser still healthy enough to put up a fight is still little more than a mindless, drooling animal. After killing them all, Alex and the rest of his group decide that nothing short of burning the entire building down will suffice to clean the filth away.
- In The White Rabbit Chronicles, the only way to truly end a zombie is with fire from a slayer's hands. At the end of ''Through the Zombie Glass', the slayers use their fire to kill "Zombie Ali".
- In the Young Wizards series the spiritual entity which empowers the Spear of Light, the Virtue of Purification, is associated with the element of fire. It can burn away the impurities and imperfections of any living being, but the process of doing so is lethal. The Spear does not care that purifying things destroys them (as one character says, patience is not one of its virtues), so it's a good thing that the Spear can't throw itself.
- Fire is used to purify remains in Supernatural. Salting and burning the bones of a person or burning any other earthly remains (hair, fingernail, teeth, etc.) is often the only way to put a vengeful spirit to rest.
- Tears for Fears: "Badman's Song" evokes this trope with the verse "Fire can cleanse your soul".
- This is a common theme in The Bible. Whether it's total destruction of wickedness, as is the case with the city of Sodom, or simply refinement of believers, fire seems to be one of God's favored tools.
John the Baptist: I indeed baptize you with water; but One mightier than I is coming, whose sandal strap I am not worthy to loose. He will baptize you with the Holy Spirit and fire. His winnowing fan is in His hand, and He will thoroughly clean out His threshing floor, and gather the wheat into His barn; but the chaff He will burn with unquenchable fire.
- The concept of purgatory in Catholicism, where believers go to be cleansed of their sins after death before they are allowed to enter into Heaven, since according to the Book of Hebrews, no one will see the Lord without holiness.
- Zoroastrianism depicts fire as associated with Ahura Mazdha and being inherently good and purifying, likely because Ahriman is associated with darkness, and fire is a commonly used as a light source.
- In The Magic Flute, Tamino and Pamina's final initiation trial is to walk through fire and water and be spiritually purified by them. Thanks to the magic of the flute, they're able to do so without being harmed.
- Used classically straight in Dungeons & Dragons when dealing with green slime. Fire is one of the few things that will kill it, and burning it off while it's still busily trying to turn your comrade's flesh into more green slime is about the only way to save them if you don't have just the right healing spell handy at the moment.
- This, in a nutshell, is the Circle of Wildfire Druids shtick in 5th edition. Along with a suite of fire spells like Burning Hands, Scorching Ray, and Flame Strike, the subclass gets bonus spells that are themed around healing and growth (Cure Wounds, Revivify, Plant Growth) and the ability to conjure a Wildfire Spirit that can either heal allies or harm foes. The flavor text emphasizes that wildfires are a healthy part of the natural order, scouring the land clean to make way for new growth.
- Magic: The Gathering:
- White is usually the color of purity, but Red occasionally gets a cleansing motif, such as Cleansing Beam or Burn the Impure.
- Maniacal angels can be associated with either White or Red mana, culminating in Avacyn, the Purifier.
- Amonkhet's Red-aligned god Hazoret uses "cleansing fires" to clear her mind of Bontu's corruption.
- Nexus magazine #3 article "Land of the Pharaohs". The Purifying Flames spell will remove a curse or guilt from a person who enters the flames.
- Warhammer 40,000:
- Among the Imperial forces, flamers are usually seen as a good metaphor for purifying the God-Emperor's enemies. Sisters of Battle take it even further, with most squads wielding flamers or wearing hats that are on fire. Not to mention virus bombing (which basically converts a large proportion of the planet's surface into fuel and strikes a match).
- The incinerators flamers used by the daemon hunting Grey Knights enhance the widely held belief in the purifying effects of fire with the addition of sacred oils to its already highly blessed fuel to make them especially dangerous to the Chapter's daemonic enemies. Some editions of the rules represented this by giving incinerators bonuses such as the ability to ignore the invulnerable saves of daemonic creatures.
- It's also effective when dealing with Orks for more practical reasons; they're fungus based lifeforms which release spores (which eventually grow into new orks). Burning them helps prevent them reinfecting planets they've attacked.
- The Firemen of BioShock Infinite certainly seem to think so, given their constant claims that FIRE CLEANSES!
- In the good ending of Cuphead, after defeating the Devil, Cuphead and Mugman toss the Soul Contracts into the fiery furnace to incinerate them (since the Soul Contracts indicate that the inhabitants of the Inkwell Isles lost their casino games against the Devil who until now owned their souls, though they skipped out on paying their deals to him and were deep in debt). In destroying the contracts in this way, the boys deliver the grateful inhabitants from eternal servitude to the Devil.
- Freddy Fazbear's Pizzeria Simulator serves as a Grand Finale of the Five Nights at Freddy's franchise. In its true ending, earned by salvaging all four of the scrapped animatronics, you listen to a message from the Cassette Guy who hired you directed to both yourself and the animatronics. As he speaks of finally ending the nightmare once and for all, images are shown of Scrap Baby, Molten Freddy, and Springtrap burning, with particular malice directed from the Cassette Guy to Springtrap. The obvious intent is to destroy everything beyond hope of recovery and finally put all the lost souls involved to rest.
- The Insanity Ending also provides an explanation as to why Fire Purifies: the souls are bound to the animatronics (or, in one case, an empty skinsuit) by a substance called remnant. This substance breaks down at high temperatures, meaning fire is truly the only way to purify.
- In Serena, the titular character burns down the cabin she murdered her husband in. This is a wise choice — the flames destroy not only evidence, but his ghost.
- A sidequest in Silent Hill: Downpour involves setting fire to the picture of a man who murdered his family, allowing their spirits to rest.
- In Tales of Zestiria, Lailah is able to use the Flames of Purification to stop Hellions and purify Malevolence. Its later revealed this is because of a pact she made with Maotelus. Tales of Berseria later provides an origin to this ability: It was a special flame created by a Malak named Laphicet, who became Maotelus.
- In Warframe, Nezha's Fire Walker ability leaves a trail of fire along the ground as he moves. In addition to setting enemies alight, contact with the flames cures allies of status ailments.
- In World of Warcraft, after a battlefield was covered in a weaponized Plague, a group of red dragons use their fire breath to destroy the lingering disease before it could permanently poison the land. Afterward, rather than scorched, blackened earth, the ground is coated in newly-sprouted plant life.
- Long before there was any scientific germ theory to explain disease, humans had learned that fire made rotting corpses and things that had been in contact with sick people and animals harmless. If cleaning infectious things with water didn't work, fire would do the job as a last resort, which makes fire the ultimate form of purification in cultures all over the world.
- Zoroastrians regard fire as a symbol of purity... but in a way that historically has tended to avert this trope — fire is pure, but burning the impure was more likely to taint the fire than purify the impure (hence the scarcity of cremations).
- Heretics were burnt alive because it was believed that death by fire purified the soul.
- Cooking in general, as the high temperatures of the fire or grease used for most foods will kill most of whatever germs are in the raw meat, making it safe to eat without fear of becoming poisoned.
- Cauterizing (burning flesh usually with heated metal or a strong acid) can be used as a last resort to stop bleeding or prevent a wound getting infected ("last resort" because this burning will kill the surrounding flesh).
- In microbiology, an important step in culture-plating (to prevent your petri dish from growing bacteria/fungi you didn't intend to grow), is to run the metal loop used to spread the culture through a flame. (However, some labs have switched to single-use plastic loops, eliminating this step.)
- Supposedly, Emperor Charlemagne owned a tablecloth which he would throw into the fire after a banquet. It would glow red-hot but not burn, and to the astonishment of his guests, he would draw it out to reveal that it was not only intact, but far cleaner than could be managed by simple washing. This was because it was made of asbestos, the health risks associated with the substance being unknown at the time. Don't Try This at Home. (Similar accounts have been recorded from all over the world — one Chinese general is said to have owned a jacket made from it, which he would "accidentally" spill wine on and throw into the fire in feigned disgust, as a party trick.)