->''"For the soul of every sort of flesh is its blood by the soul in it. Consequently I said to the sons of Israel: 'You must not eat the blood of any sort of flesh, because the soul of every sort of flesh is its blood. Anyone eating it will be cut off.'"''
-->-- '''{{God}}''', ''[[Literature/TheBible Leviticus 17:14]]''

Blood. Animals have it, humans have it, even [[AlienBlood aliens have it.]] There's just something about the red liquid that flows through our veins that makes it seem important. Probably something to do with that whole..."keeping us alive" thing it does so well. As such, in fiction, it tends to have one or more of these properties.

* A) '''[[BloodOath Blood is binding]]''' -- Any {{Magically Binding Contract}}s made in blood ''must'' be honored, on pain of death, even if the contract was only written in blood because you CouldntFindAPen. If you make a BloodOath, and swear that "if you break your word, may the earth drink your blood!", and break your word anyway, you may find yourself six feet under.

* B) '''[[SymbolicBlood Blood is symbolic]]''' -- Blood may be used as a stand-in, or weaker form of souls, life force, what have you. Alternatively, other things may be used to symbolize ''it''. The latter applies to things like an android's oil being sprayed out like it's HighPressureBlood.
** For examples of the latter, see AlienBlood or SymbolicBlood.

* AB) '''[[BloodMagic Blood is magical]]''' -- Any spells that require [[EyeOfNewt blood as a reagent]] will probably be either extremely powerful, BlackMagic, or both. Since blood is basically LifeForce, [[PowerSource anything using it]] will work similarly to things CastFromHP, or it may be used to [[FertileBlood create life]]. The blood of [[MainliningTheMonster especially powerful or arcane creatures]] may compel others, grant immortality, or even [[BodyToJewel become gems]].
** See Also: BloodBath

* O) Most importantly, '''[[BloodyHorror Blood is ]]''[[BloodyHorror disturbing]]''''' -- There's just something about blood leaving the body that generally freaks people out, either from fear or disgust. For obvious reasons, it's directly associated with pain, injury and death. {{Horror}} and [[SlasherMovie Slasher]] stories rely on this. A further division of this, often connected to A, B, or AB, are messages written in blood, which are used primarily to scare the bejeezus out of people, but may also have magical, symbolic, or binding properties. This is sometimes combined with RoomFullOfCrazy for the extra creepy. Properly used, blood can turn fear into PrimalFear - as per the shower scene in ''Film/{{Psycho}}'': the sight of Janet Leigh's hand trailing slowly down the shower curtain - scary. The blood (actually just ''chocolate syrup'') smearing under her fingers - PSYCHO! Many movies overdo this, resulting in mere {{Squick}} - ''Film/SilentHill'' pours on the tension until your heart threatens to explode from your chest - scary. Then Pyramid Head shows up and tears the skin from a woman in a single tug - not that scary, just your basic {{Gorn}}.

Now, remember: Type AB Blood Power draws off of all the others, and all of them draw from Type O. Just be aware of the donor; may contain [[BloodyHilarious Bloody Hilarity]]. Has nothing to do with ThePowerOfCheese.


!Type A
[[AC:Anime and Manga]]
* It's explicitly said in ''Manga/ChronoCrusade'' that when Chrono [[DealWithTheDevil made a contract]] with [[spoiler:Mary Magdalene, his first contractor]], that she had to give him some of her blood to complete it. It's implied (using vampire imagery) that this was also the case with his contract with Rosette.
* ''Anime/TheVisionOfEscaflowne''. The movie version took it UpToEleven
* ''Anime/EurekaSeven'': [[spoiler:coming of age rite to calm the planet, ISN'T NICE]]
* In ''Manga/{{Naruto}}'', to summon animals one must first sign a summoning contract. It requires that the user must sign it in his/her name in their own blood followed by a fingerprint stamp in blood as well.
* The ultimate use of her power to [[spoiler: unite humanity into a single being]], Charlotte B. Lord of "Anime/UnlimitedFafnir" can use massive amounts of her own blood to control other people over a wide area, with the controlled adding their blood to the equation in a positive feedback loop that could involve the entirety of humanity.

* FanFic/AGrowingAffection has a BloodOath Jutsu, which is absolutely binding. Whatever a person sets as the penalty for breaking the oath, his or her own body and chakra will make happen.

* In the film ''Mongol'', young Temudgin makes a blood oath with Jamukha, who saved his life. This makes Jamukha the brother to Temudgin, and in the end, [[spoiler: Temudgin lets Jamukha go, even though he proves to be a threat in the future, saying that he's not sparing an enemy, he's freeing his brother.]]
* Being 'blood brothers' is part of many westerns.
** Film/McLintock
* In ''Film/PiratesOfTheCaribbeanTheCurseOfTheBlackPearl'', the blood of those who took coins from the Chest of Cortez (or that of their children)is required in order to end the curse.
* Being deemed negro was an important plot point in ''Theatre/{{Showboat}}''. By sharing a drop of blood, the hero was now deemed negro and could marry his sweetheart without violating the miscegenation laws.
** Note that this wasn't, strictly speaking, either a legal or magic thing: his sweetheart was mulatto (half-black, half-white). He cut her finger and sucked out a drop of blood so that he (and the people who witnessed it) could say that he "had negro blood in him" without actually ''lying.''

* In ''Literature/DaughterOfTheLioness'', an oath sworn in blood kills anyone who breaks it, with the blood boiling in their veins. It's not much favored in Tortall due to the nastiness of it, but Aly happily exploits it when forcibly recruiting spies from the enemy in the Copper Isles.
* Marie Brennan's ''Literature/{{Doppelganger}}'' duology features a blood-oath as a plot point in both books. If the oath is broken, the magically-sealed scar will bleed the Hunter ([[spoiler:or witch or Cousin in the second book]]) to death through one wrist. Unique in that the oath binds both parties to their word (presumably; the actual wording states that the contractor binds him/her''self'' to grant the contractee three boons without conditions, so magical compulsion may or may not extend to the contractor). Also a slight crossover with Type AB, as blood is used not only to bind the contractee, but as an elemental focus for shaping the complicated spell, and while it represents Fire in the blood-oath spell, it is "one of the rare foci that can serve for more than one."
* In ''Shadows For Silence In The Forests Of Hell'', by Creator/BrandonSanderson, shedding blood will draw the wrath of the shades like nothing else. An accidental bump or nosebleed doesn't count, but blood shed in anger, exposed to the air, will enrage every shade in the vicinity. First, they will hunt down and kill whoever shed the blood, then, being enraged, they'll kill anyone else that happens to be nearby.
* The hundred gods in ''Godslayer Chronicles'' by [[Literature/SigmaForce James Clemens, AKA James Rollins]], in contrast with the rogue gods, became the hundred by binding themselves to the land. This was done by spilling massive amounts of their own blood upon the ground. The act purged them of the insanity of the rogue gods, but forever confined them to an area within an unspecified radius of where they spilled their blood. Any god that leaves its realm or enters another's realm (including rogue gods entering a realm of the hundred) bursts into flames and dies.

* In both ''TabletopGame/VampireTheMasquerade'' and ''TabletopGame/VampireTheRequiem'', vampire blood is highly addictive to both vampires and mortals. The eponymous Blood Bond is formed when someone drinks three times from the same Vampire within a period of time, and forms such an intensely emotional and psychological bond in the drinker that it becomes difficult for them to willfully do anything which could cause even distress or disappointment in the host vampire.
* TabletopGame/{{Warhammer 40000}}:
** The Grey Knights keep a massive library containing the true names of daemons, each written in an Imperial servant's blood one syllable at a time per copyist to prevent the daemon from having power over the book it's kept in.
** Ironically, Khorne the Blood God is a WarGod who despises magic users as cowards, thus magical blood is averted for his troops.

%%* Two words: Theatre/DoctorFaustus.
* Averted in ''Theatre/DamnYankees'', where [[LouisCypher Applegate]] laughs at the idea of having Joe sign his name in blood to the [[DealWithTheDevil contract]].
* ''Theatre/{{Showboat}}'', as described above.

[[AC:Web Comics]]
* In ''Webcomic/SluggyFreelance'' only Gwynn can use [[TomeOfEldritchLore the Book of E-Ville]] to cast spells because her name has appeared on the inside cover written in blood. Right above instructions to, if lost, drop in any mailbox to return it to the rightful owner.
* In ''Webcomic/{{Sinfest}}'', [[http://www.sinfest.net/view.php?date=2000-01-19 Satan wants the forms and waiver filled out in blood, of course.]]
* In ''Webcomic/{{Homestuck}}'', Sburb's Blood aspect is introduced with the troll Karkat, the Knight of Blood. Despite the name [[IThoughtItMeant suggesting]] a [[BloodKnight specially vicious fighter]], it refers to his role as TeamMom.
** Taken even further with [[spoiler:his ancestor [[CrystalDragonJesus The Sufferer]], who was the Seer of Blood in troll's Universe previous iteration]].
** Inverted in that blood color in troll society determines the caste, thus [[FantasticRacism causing division]].

[[AC:Web Original]]
* ''Literature/WhateleyUniverse'' example: [[EldritchAbomination Carmilla]] and [[TheFairFolk Fey]] made a blood pact that was so powerful it gave them some of the other's traits. Carmilla now has Fey's body (including PointyEars) and hair, and Fey got some of Carmilla's mental capacity.

* The idiom "blood is thicker than water". Exactly what this means has had a few different definitions over the centuries, but the binding aspect is always clear.

!Type B
[[AC:Anime and Manga]]
* In ''Manga/FullMetalAlchemist'', Ed and Al use drops of their blood to stand in for "information of the soul" when trying to bring back their mother from the dead using alchemy.
** Philosopher's Stones also [[StatesOfPhlebotinum comes in various forms]]. Solid, liquid, they're all blood red.

* In an extension to the ''TabletopGame/VampireTheMasquerade'' example above, the Kuei-Jin, the Asian equivalent to Vampires, live on life-force. The weaker ones drink blood simply because that's the easiest way to get at somebody's life-force. The stronger ones can straight-up [[YourSoulIsMine eat your soul.]]
** Notably, western vampires have a derangement called Sanguinary Animism that makes them ''think'' they do the same thing as the Kuei-Jin. Sufferers hear the voices of people they've drunk from in their heads, and believe that if they ever drink a mortal to death they also consume their soul. This essentially causes the vampire to suffer from SplitPersonality (and not the fun kind) when they drink blood.
** When it comes to [[BloodMagic Thaumaturgists]], the basic in-universe mechanics of the art requires both Paths and Rituals to have some way to "target" the subject of the power. With most Paths, it's as easy as being near enough to see the target. With rituals - which could take minutes, hours, or even days of preparation - there's got to be something on hand to establish what - or more importantly who - the magi is going after. And there's nothing that ensures a target lock like having a sample of the victim's blood. Except maybe knowing the victims True Name, but that's difficult to learn.
* ''TabletopGame/{{Warhammer 40000}}'': One of the main tenets of the Khornate religion ('''BLOOD FOR THE BLOOD GOD! SKULLS FOR THE SKULL THRONE!''') is that their god demands blood, no matter whose, as long as it's obtained through combat.
* One of the Liminal {{TabletopGame/Exalted}} castes is blood. Given that the Liminals are basically reanimated corpses, this is quite fitting.
--> '''[[WordOfGod John Morke]]:''' '''Aspects of Blood''' are born of [[MadScientist creators]] driven by “possessive” passion—lust, greed, and ambition. Blood represents the heat of passion and the wonder of emotion. Blood is a carrier as well as a fulcrum; it can be a river of plagues or a font of virginal purity with which to attract and bind the foulest of horrors and bid them whip. Blood Aspects are sanguine, passionate, outgoing creatures.
--> Blood Aspect magic, for example, may allow a Liminal to easily track a man for hundreds of miles with only a sample of bodily fluids to work from, but it also allows confident navigation of the dark waterways and torrential courses of the Underworld, as well as influence over the desires and addictions of others.

* In the ''Literature/SwordOfShadows'' series, blood is sacred to [[ProudWarriorRace the Sull]], who bleed themselves as a form of offering to their gods. Obviously, most Sull become ''very'' skilled at letting blood with minimum pain and without hitting anything important.

!Type AB
[[AC:Anime and Manga]]
* In ''Anime/PrincessTutu'', Drosselmeyer wrote a story in his own blood [[spoiler:to control the town where the anime takes place]].
** Also, the Raven is so evil that his blood can [[TheCorruption turn people evil]] when they ingest it, [[BloodBath bathe in it]], or have it otherwise go into their body.
* The jousei manga ''It's Not Like That, Darling'' uses a more passive form of this trope (a combination of Type B and Type AB). The main character gets a blood transfusion after an accident in the backstory. Later, the donor dies in another, unrelated accident and our heroine finds herself having the ''strangest'' thoughts... A tolerably good romantic comedy, as such things go.
* The entire combat system is ''Manga/DeadmanWonderland'' is based around the titular Deadmen using their blood as weapons in various ways.
* In ''Manga/MahouSenseiNegima'', [[OurVampiresAreDifferent Evangeline]], who was [[PowerLimiter de-powered]] into being stuck on the [[ElaborateUniversityHigh school's campus]] by Nagi [[RedBaron the Thousand Master]] says an ample (probably fatal) drinking of blood from him or one of his relations will somehow lift the curse.
** It's stated (at least in the English translation) that an alternate method of executing a Pactio is "open veins, swap blood", but that's not as FanService-y as kissing, so it's never actually been done that way.
** Even later, Negi learns a [[BloodMagic spell that requires him to bleed]] before he can use it, although that may be only in it's incomplete form. He uses the full version later and doesn't bother with the blood.
* In ''Manga/BlackCat'', Sheldon's Tao is manipulating blood.
* In ''Manga/FullMetalAlchemist'', Ed uses his blood to draw the alchemical seal which binds Al's soul to the suit of armor. Apparently, being produced in a living body and rich in iron makes blood a good intermediary between souls and steel.
* ''Manga/{{Hellsing}}'', where it has slight crossover with Type B when referred to as "the currency of the soul." What it means is that vampires like Alucard absorbs their meals' souls when they consume their blood. Seras discovers this truth when she consumes Pip's blood, collecting his soul, becoming a true vampire, and herself gaining some of the Power of Blood. Later, it's revealed that [[spoiler:the huge amount of souls he's consumed fuels his absurdly powerful HealingFactor--and that he can release his victims as a macabre army of the undead]].
* In Creator/RumikoTakahashi's ''Manga/MermaidSaga'', mermaid flesh can, if you're ([[WhoWantsToLiveForever un]])lucky enough to survive eating it without becoming a [[TheCorruption Lost Soul]], turn you immortal. But in the "Mermaid Forest" story, all that Sawa has is a flask of mermaid blood to heal [[IncurableCoughOfDeath her sister's illness]]. It made Towa immortal, but deformed her arm like a Lost Soul's, and now she regularly replaces it with arms cut from the fresh corpses of young women.
** [[ShoutOut Referenced]] in ''Manga/HellTeacherNube''. Here, flesh from the (still living) mermaid Hayame has a 100% success rate, and her blood can instantly heal ''any'' injury no matter how grave, without conferring immortality. It does have the side effect of making the recipient into a moron for a short while, seeing as it comes from [[TheDitz Hayame]], after all.
* One of the Contractors in ''Manga/DarkerThanBlack'', Wei, is able to teleport away anything that is covered in his blood. This power is frequently used to create gaping holes in the torsos of his enemies. Naturally, the only way he can use this power is by [[NightmareFuel carrying a knife and cutting his own wrists to toss blood on opponents.]] In case you couldn't tell, [[BadPowersBadPeople he's a bad guy]].

* In ''[[ComicBook/TheSandman A Game of You]]'', menstrual blood is used to power a spell to send the characters to the land of the dead and come back alive ([[spoiler:mostly]]). In ''The Time Of Your Life'', the same spell is powered from blood from Foxglove's hand.
* Another parody happens in ''ComicBook/LenoreTheCuteLittleDeadGirl'', when she pricks her finger and spills a drop of blood on a doll. It turns out to be a vampire that was cursed to be an inanimate plaything, and her blood broke the curse. Unfortunately, he realizes he's still in a doll's body because the curse didn't break properly; she'd been embalmed.
* ''ComicBook/{{Runaways}}'': "When blood is shed, let the Staff of One emerge."
* In ''Creator/DetectiveComics'' #833 Zatanna is shot in the throat by the Joker and dunked into a tank filling with water, effectively keeping her from reciting her incantations backwards. When Batman escapes his own deathtrap to free her in #834, he finds her throat completely healed. Upon inspection, Bats discovered she'd used her own blood to write "HEAL ME" backwards on the inside of the tank's lid.
--->'''Batman:''' ''A spell written in blood. For a mage like Zatanna, no enchantment is more powerful.''

* FanFic/AGrowingAffection: Naruto's Blood Clone Jutsu, a dangerous technique that uses blood to create stronger clones.
* ''Fanfic/ChildOfTheStorm'' and its sequel, ''Ghosts of the Past'', draw on both ''Literature/HarryPotter'' and ''Literature/TheDresdenFiles'', particularly the latter, in their use of blood magic. While it isn't necessarily dark magic, and can be used benevolently to enhance spells, empower rituals and magic circles, and enforce bindings, it ''does'' stray very close to that area, and is much favoured by vampires - especially the Red Court and, to a lesser extent, Dracula's Grey Court. As a consequence of the latter, [[CrazyPrepared Doctor Strange]] has Harry study up on it extensively when he's set to run into Dracula and his plan to [[spoiler: use the blood of a SuperSoldier to become, among other things, immune to sunlight]].
* ''Film/TheGoldenVoyageOfSinbad''. The wizard Prince Koura uses his own blood to create a homunculus.
* Ryuhei Kitamura's ''Film/{{Versus}}'' revolves around the "Blood of Resurrection," which the villain plans to use in the Forest of Resurrection to open some kind of a dark door and get "The Power." Zombies and reincarnated samurai are involved.
* The blood of those who took the coins from the Chest of Cortez is required to lift the curse in ''Film/PiratesOfTheCaribbeanTheCurseOfTheBlackPearl''.
* In ''PuppetMaster [[VersusTitle Vs]] DemonicToys'', a small blood sacrifice is needed to bring the toys to life. Leading to some HypocriticalHumor when the two heroes [[DiscussedTrope wonder what sort of sick person would use such magic]] before discussing which of them should provide the drop of blood.

* Melisandre of ''Literature/ASongOfIceAndFire'' uses the blood of a king in a ritual to [[spoiler: cause the deaths of Robb Stark, Joffrey Baratheon, and Balon [=GreyJoy=]]]. [[MaybeMagicMaybeMundane Possibly.]] The maegi Mirri Maz Duur also uses blood magic to [[spoiler: [[EmptyShell "heal"]] Drogo]] and the favor is returned by Daenerys when she [[spoiler: burns the maegi alive as part of the magic to awaken her dragons.]]
** This was also part of the Targaryens' reasoning for their [[IncestIsRelative rampant incest]].
* Creator/MercedesLackey loves this concept, and blood mages are frequently villains in her books. Combines with Type O, since the shedding of blood is incidental -- the suffering and trauma of the victim is the real source of power.
** There are also good people who use blood magic--they only use their own blood. Most notably, the [[Literature/HeraldsOfValdemar Shin'a'in]], whose patron goddess will sometimes require someone (usually a shaman) to sacrifice themselves to prove the people's need.
* In ''Literature/{{Stardust}}'', the witches use the hearts of living stars to prolong their youth as a form of blood magic.
* In ''Literature/HarryPotterAndTheGobletOfFire'', Voldemort uses [[spoiler: Harry's blood to reconstitute himself]]. In addition to reviving himself, it gives Voldemort the power to touch Harry, because [[ThePowerOfLove the all-sacrificing love]] that Lily imparted to her son resided in Harry's blood. This later[[spoiler: backfired as the blood link to the then-immortal Voldemort prevented Harry from dying, though this]] didn't stop a rebounding Killing Curse later on.
** Also, in ''Literature/HarryPotterAndTheHalfBloodPrince'', a small blood sacrifice is needed [[spoiler: to reach the spot of Voldemort's Horcrux. Dumbledore actually expresses disappointment at Tom Riddle for such a basic idea (that overlaps with Blood Is Scary, below), and points out to Harry that the idea is to weaken the intruder as much as possible.]]
** And then there's unicorn blood. It will, according to Firenze, "keep you alive, even if you are at the brink of death, but at a terrible price. You have slain something pure and defenseless to save yourself, so you will have but a half-life, a cursed life, from the moment the blood touches your lips."
* ''Literature/{{Discworld}}'' parodies this with the Rite of Ashk'Ente, which summons Death - it's implied that this is supposed to require a human sacrifice, but magical refinements mean that it's now possible with only "4 cubic centimetres of mouse blood".
** In ''Discworld/CarpeJugulum'', Granny Weatherwax uses this kind of blood magic against vampires by [[spoiler: 'infecting' ''them'' when they feed on her.]]
--->[[spoiler: I aten't been vampired. You've been Weatherwaxed.]]
* In ''Literature/TheChroniclesOfAmber'' series, the mystic Pattern that created the universe was drawn in the blood of its creator. The discovery that the blood of his descendants could ''erase'' it drives part of the plot.
* In the ''Literature/CodexAlera'' series, the Alerans have magical creatures living inside them that give them elemental magic powers. The werewolf-like Canim don't have inherent magic like that. So they drain blood from freshly dead sentient beings, and use that to cast magic. The magic is appropriately creepy, and destructive. One creates clouds of acidic mist, another summons tentacled horrors from midair which are also acidic or at least venomous, and a third calls down lightning on chosen targets. All of these require the spilling of blood. However, it is stated that ritualists are also their peoples' priests and doctors, so presumably they have more benign spells that we don't see because we only see them during battles. In addition, some Canim use the blood of their enemies to fuel spells and sometimes kill civilians specifically for their blood, but more noble ritualists only use blood from volunteers or ''their own''.
** On the 'Night of Red Stars', the Canim ritualists cast a spell that puts acid mist clouds full of [[EldritchAbomination weird seemingly extradimensional tentacle monsters]] over a good part of the ''continent'', preventing the Alerans from flying (since they get eaten/dissolved if they try to go through the clouds). But this huge spell is said to cost ''millions'' of Canim lives.
* ''Literature/TheDresdenFiles'' has this trope down to a ''science''. Blood can power rituals, keep curses alive through generations, fuels Red Court Vampires, can be used to track someone or otherwise create a symbolic link to them on which to do magic.
* The Mosquito-kinden of ''Literature/ShadowsOfTheApt'' have a ''serious'' thing about blood, and huge quantities turn up in some prophecies.
* Also from ''Literature/SwordOfShadows'', it's possible for weaker sorcerers to enhance their powers by draining blood from a properly bound stronger sorcerer. [[EvilOverlord Penthero Iss]] demonstrates both the binding and the bloodletting in NightmareFuel detail.
* In the ''Literature/OldKingdom'' trilogy by Creator/GarthNix, the power of the Charter that gives the King, Abhorsen, and Clayr their unique abilities is found InTheBlood - as in, both genetically and literally. Charter Stones, which keep the magical Old Kingdom sustained, can be broken if a Charter Mage's blood is spilled on them (in death), and the [[CosmicKeystone Great Stones]] can only be broken by the blood of one of the Charter bloodlines (see above.) Finally, in ''Abhorsen,'' [[spoiler: Sam makes a sword to break apart the EldritchAbomination by combining, among other ingredients, blood from carriers of all [[strike: three]] four bloodlines.]]
* In one of Tamora Pierce's ''Literature/CircleOfMagic'' books, Niko cuts his palm so that he can use his own blood to fuel a past-viewing spell, saying that mages will often use blood to make a spell more powerful. He then says some use their own, others use the blood of others - willing or not - and sternly warns the student listening to him not to use others.
* Some cross-over with Type A in the ''Literature/ChroniclesOfTheKencyrath'' with blood-binders- Kencyr who have the inherent magical ability of creating a telepathic link with anyone who's exposed to their blood, a link that is so powerful that can endure past death. [[OurVampiresAreDifferent Darkling Changers]] have a related ability of being able to take the form of anyone whose blood they've sampled. If a Changer tries to feed on a blood-binder, and the blood-binder's magic is stronger, then the Changer will be wracked by intense pain, the only known release form which is death.
* ''Literature/TheElenium'' plays with type AB. In this case blood isn't so much magical as it is innately capable of ''restraining'' magic. The living stone Bhelliom is supposedly controllable by two rings, each of which contains pieces of the original Bhelliom stained red with blood. Later, it's revealed that blood restrains Bhelliom for a very prosaic reason: [[spoiler:Bhelliom cannot stand the touch of iron, and human blood has iron in it]].
* In ''Literature/TheWheelOfTime'' series by Robert Jordan, we have the mindtrap; similar to a phylactery. Combined with the blood and saliva of a channeler(magic user), it captures the soul, or essence of said channeler. Should this fragile item be crushed in someone's hand, the holder will have complete control over the (now)mindless puppet.
* In ''Literature/NewArcana'', only people with mageblood can use arcane magic, and mageblood is a street drug. The Order's soul-binding ritual involves mingling the blood of the cohort members.
* In ''Literature/{{Pact}}'', blood is symbolic of the self, and can therefore be used as a source of power in an emergency-but only the mad or the desperate do this, because spilling blood is spilling the self, and a lot of Others ''like'' it when people are hollowed out shells-it gives them room to move in.
* In ''Literature/TheWitchlands'', Bloodwitches can distinguish people by the smell of their blood and track them down by it even across open sea. They can also control blood in other people's veins, letting them, for example, freeze them in place or stop their hearts.
* In the ''Godslayer Chronicles'' by [[Literature/SigmaForce James Clemens, AKA James Rollins]] there are 9 bodily fluids[[note]]Blood, Sweat, Tears, Saliva, Phlegm, Semen, Menstrual Fluid, Shit, and Piss[[/note]] or "humors" that are given by the gods, which hold the god's powers and are combined in various ratios to produce magic. The one rule to mixing is that blood must always be present, it functions as the activator and no magic can exist without it. Therefore it is also the most sacred and closely guarded of the humors.

* Seeing as it provided a title quote it's not surprising that ''Series/BuffyTheVampireSlayer'' has a few examples of this. The blood of a slayer apparently has mystical qualities, allowing Angel to survive Faith's poison, and granting the Master the strength to escape his prison in the first season. Dawn's blood was used by Glory to open the interdimensional portal.
* ''Series/{{Angel}}'' also used this quite extensively. The Beast dripped blood onto the artifacts it had gathered as the final part of its ritual to blot out the sun. The blood of a virgin was used to expedite the birth of Jasmine. Lorne's blood was used in another ritual calling for the blood of a demon. And of course Hamilton's blood turned out to be full of the power of the Senior Partners. There are probably a lot more. Any show with vampires and magic is likely to feature a lot of this trope.
* In the ''Series/DoctorWho'' episode "The Christmas Invasion", the Sycorax use samples of A Positive that they took out of a satellite to control everyone in the world of that blood type.

* As Richard Carrier memorably put it: "God needed blood to fix the universe, but only his own blood had enough magic so he gave himself a body and killed it".

* In the ''TabletopGame/{{Shadowrun}}'' supplement ''Aztlan,'' mages can use BloodMagic: spilling a human's blood to enhance spellcasting and summon Blood Spirits. Extremely evil, restricted to Non Player Characters.
* ''TabletopGame/DungeonsAndDragons'': One of the material components for the Cacodemon spell (which summoned a powerful demon) was a bowl of mammal blood, preferably human.
** In-character folklore (well, [[TheRashomon one version of it]]) of the default D&D pantheon holds that elves and orcs were born from the blood of their respective creator-deities, Corellon and Gruumsh, which got spattered across multiple worlds when their deities were fighting a death-duel (both survived, however).
* Common in the TabletopGame/{{Ravenloft}} setting, both as a power-source for certain kinds of evil magic and as a means for vampires to bequeath temporary vigor and prolonged life to their mortal minions.
* ''TabletopGame/{{Exalted}}'' uses this trope in several places. Lunar Exalted gain their myriad of [[ShapeShifting forms to pick from]] by hunting the creatures they seek and drinking their heart's blood; Abyssal Exalts can recharge their power [[OurVampiresAreDifferent by drinking blood]]; and several sorcerous (and all necromantic) rituals also require the sacrifice of blood in the process of casting. Sometimes [[CastFromHitPoints from the caster him/herself.]]
* As mentioned above, both ''[[TabletopGame/VampireTheMasquerade Vam]][[TabletopGame/VampireTheRequiem pire]]'' games take full advantage of this subtrope. Once blood enters a vampire's body, it becomes something ''more'' than blood (often referred to by vampires as "Vitae").
* In ''TabletopGame/LegendOfTheFiveRings'', "Bloodspeakers" practice a very evil type of magic, powered by blood that is usually (though not always) unwillingly donated by others, who typically don't survive the experience.
* In ''TabletopGame/{{Rifts}}'' and the Palladium universe, blood sacrifices are common for most kinds of magic because P.P.E. doubles at the time of death. But the actual representatives of this trope are Blood Shamans, who cast grisly spells from their own blood with a bit of Casting from HP.
* The Whateley Family in ''TabletopGame/{{Deadlands}}'' have this as their hat. It is CastFromHitPoints, is powerful and overuse does Very Bad Things. The Whateleys are for the most part inbred, insane, powerful, rich and servants of the BigBad.

* In the ''VideoGame/{{Dominions}}'' series, spells from most schools of magic are cast using "gems" which are basically elemental forces (fire, water, etc...) concentrated into portable form, and the casting prices of spells are listed in these gems. Instead of gems, however, one school of magic lists spell prices in blood. These prices are listed in increments of one ''blood slave'', each of which must be drained completely empty, with high-level spell costs running into the ''hundreds''.
** And true to the trope, blood magic is enormously powerful. Going deep into blood magic and relying completely on the armies of demons it allows you to summon is a valid strategy all by itself. Some of the strongest nations in the game are that way because of how well-suited they are to that strategy.
* ''Franchise/DragonAge'':
** BloodMagic, which uses CastFromHitPoints types of magic (and not necessarily the caster's hit points). A Tevinter Imperium blood mage even uses his own [[BadBoss henchmen]] as sacrifices, usually by making them explode with the words "A blood sacrifice! For power!"
** "Reavers", a particularly dangerous type of warrior that become stronger through suffering and exhibit certain magical powers, are created by drinking the blood of dragons. There are entire cults that spring up around high dragons for this reason. Some members of the [[HornedHumanoid Qunari race]] have been known to develop Reaver abilities purely through training. The [[DraconicHumanoid implications of this]] have not yet been fully explored.
*** Grey Wardens themselves are created by drinking a special cocktail of darkspawn blood and lyrium, which makes them immune to the [[TheCorruption darkspawn taint]] [[spoiler:for a few decades, anyway.]] It also gives them the ability to sense the darkspawn [[spoiler: though the darkspawn can sense them as well.]] The Warden's Keep DLC also confirms that Grey Wardens can gain other abilities through their tainted blood.
* In ''VideoGame/WorldOfWarcraft'' death knights have power over blood. Those that specialize in it can apparently suck blood they've lost back inside them through [[http://cata.wowhead.com/spell=49998 Death Strike]] (or possibly drain it from their enemies into themselves, how it's supposed to work isn't entirely clear), create a "blood shield", boil the blood of the enemies, and create bloodworms to attack their enemies. Which ''burst'' from gorging themselves, healing nearby allies through a mechanism that appears to be ''showering them in other people's blood''. All in all it's pretty [[{{Squick}} Squicky.]]
* This is part of the plot to ''VideoGame/ZeldaIITheAdventureOfLink''. Link killed Ganon in the [[VideoGame/TheLegendOfZelda original game]], but several of his minions are still running amok in Hyrule. While he goes on the eponymous adventure to return six crystals to six palaces, he has to be careful; the minions want to kill him so they can scatter his blood on Ganon's ashes and return him to life.
* In ''VideoGame/VanguardBandits'', the [[EvilWeapon monstrous Zulwarn]] [[AMechByAnyOtherName ATAC]] needs Blood in order to run.
* In ''VideoGame/{{Okamiden}}'', the BigBad Akuro must [[BloodBath bathe]] his [[DemonicPossession vessel]] in blood to become perfect. [[spoiler:Specifically, Orochi's blood.]] Or, maybe he has to bathe himself. The game can't agree with itself on this point.
* ''VideoGame/{{Messiah}}'': Satan feeds on human blood, which is what he needs to "physically exist in the Earthly realm"; he also seemingly derives his power from it. [[spoiler:Scientists' logs in the final level suggest that he managed to break free from his imprisonment in the research facility when they accidentally gave him too much blood to drink.]]
* In ''VideoGame/{{Touhou}}'', [[TheOjou Remilia]] [[OurVampiresAreDifferent Scarlet]] has power over blood, and possibly so does her [[StrongerSibling little sister]] [[MadWomanInTheAttic Flandre.]] Apparently she can do [[SwissArmyWeapon many things]] with it. As [[KleptomaniacHero Marisa]] [[BlatantLies so eloquently]] put it: "[[RunningGag Blood is amazing!]]"
* In Creator/CliveBarker's ''VideoGame/CliveBarkersJericho'' ([[WebAnimation/ZeroPunctuation by Clive Barker]]), the character of Wilhelmina "Billie" Church is a blood mage, whose spells can bind enemies and set them on fire. Her blood magic and abilities are also very important to certain aspects of the story.
* The Healing Church's special blood in ''VideoGame/{{Bloodborne}}'' can cure any ailment and has cemented the church's power over the city of Yharnam. [[spoiler: Too bad it belongs to/''is'' an EldritchAbomination and gradually transforms people into horrific beasts.]]

[[AC:Web Comics]]
* [[SubvertedTrope Subverted]] in ''Webcomic/SluggyFreelance''. Torg finds out that his [[EmpathicWeapon talking]] [[CoolSword sword]] [[FluffyTheTerrible Chaz]] only has its mystical abilities to speak and kill damn near anything if it has fed on the blood of the innocent first, and so assumes it's an evil sword. Chaz clarifies that it is simply a weapon, and whether it does good or bad things is entirely up to the person using it.
* Shows up in ''Webcomic/{{Underling}}''.
* In ''Webcomic/TowerOfGod'', King Zahard transfers power to Zahard's princesses, his adopted daughters, by his blood.
* In ''Webcomic/PublicHumiliation'', Pooka blood is needed to power magic runes used for all sorts of things in modern society. Originally, it was freely given by Pooka to their allies, but when they were tired, and tried to say "no more", they found that their "allies" had become just another foe. [[spoiler: Needless to say, when a Pooka hero did show up, things got messy.]]

[[AC:Web Original]]
* In the Breeniverse series ''WebVideo/Lonelygirl15'' and ''WebVideo/KateModern'', infusions of Trait Positive blood can extend the human lifespan considerably. In ''WebVideo/LG15TheResistance'', [[spoiler:Maggie]]'s blood grants total immortality.
* Fey of the ''Literature/WhateleyUniverse'' used the blood of Hekate to throw a ''major'' Sidhe curse on her: a three-fold return of all the evil Hekate had done, which (given just what we've seen) will be horrific.

* ''WesternAnimation/AvatarTheLastAirbender'' and its SequelSeries ''WesternAnimation/TheLegendOfKorra'' have bloodbending. A twisted version of [[MakingASplash waterbending]] that essentially allows the user to manipulate the blood flowing through living creatures' bodies: crushing internal organs, [[PeoplePuppets controlling living bodies like puppets]], [[spoiler:[[DePower severing chi pathways]]]]. [[WhatDoYouMeanItsForKids Ya know, for kids]]!

!Type O

[[AC:Anime and Manga]]
* In ''Manga/DeathNote'', VillainProtagonist Light Yagami kills people by writing their names in pages of a [[ArtifactOfDoom supernatural notebook]]. For emergencies, he keeps a needle and scrap of Death Note paper in a secret compartment in his watch, which means that even in tense situations where he's under surveillance, he can murder people by discreetly writing their names in [[CouldntFindAPen his own blood]].

* Franchise/SpiderMan villain ComicBook/{{Carnage}} has an alien symbiote mixed into his bloodstream that allows him to shape his blood and use it as a weapon. This is sometimes played for a more horrific effect, particularly in Creator/WarrenEllis and KyleHotz's BodyHorror laden graphic novel "Mindbomb"
-->'''Carnage''': My blood wants to kill you!

* ''Literature/{{Dracula}}''.
* [[Literature/HarryPotter Dolores Umbridge]] and her blood quill uses this, which clashes horribly with her otherwise {{Kawaiiko}} persona. It serves as one of the biggest clues to how much of a [[BitchInSheepsClothing nasty piece of work]] she really is.
* In Creator/RobertEHoward's Literature/ConanTheBarbarian story "Literature/ShadowsInZamboula" Baal-pteor offers HumanSacrifice with a NeckSnap, to save blood for the god.

* ''TabletopGame/{{Warhammer 40000}}'':
** In Creator/GrahamMcNeill's Literature/HorusHeresy novel ''Fulgrim'', the influence of the [[ReligionOfEvil Laer temple]] causes Serena to add blood to her paint in hopes of capturing the vivid colors she imagines. [[spoiler:She seduces Leopold in order to murder him for his blood.]]
** For that matter, one could count anyone who worships Khorne, the GOD of Blood.
* This is why Vampires in ''TabletopGame/{{Shadowrun}}'' attack people and drink their blood -- ''Shadowrun'' vampires actually drain [[LifeForce Essence]] to survive, but Essence Drain only works when the victim and predator are connected on a deep, emotional level. It just so happens that for most vampires, the easiest emotion to connect with your victim is "fear", and drinking someone's blood while they're watching helps tremendously.

* In the climax of ''VideoGame/{{ICO}}'', we see the only blood in the game when [[spoiler:Ico's horns snap off]]. The sudden physical sign of violence after a game full of whacking nothing but intangible Smokemen is like a punch to the gut.

[[AC:Web Comics]]
* In ''Webcomic/HannaIsNotABoysName'', Hanna's blood is apparently particularly disgusting, at least according to a vampire. He attributes this to his use of magic (before quickly changing the subject).
--> Hanna: It must be because I use magic, it taints my blood, but ANYWAYS.
* In ''Webcomic/{{Roza}}'', [[http://www.junglestudio.com/roza/?date=2007-05-03 her blood is magical]]. [[PowerGlows It glows.]]