History Main / BloodOath

* In ''Literature/TheBible'', the covenants that God makes with His people require the shedding of blood to make them effective and binding. Moses sprinkled the book of the Mosaic Covenant as well as the Israelites with the blood of goats and calves to sign and seal that covenant. Years later, Jesus would shed His blood on the cross to put into effect the New Covenant between God and His people, the Christians.

* Starting with 4th Edition, some of the Triad gangs in ''Tabletopgame/{{Shadowrun}}'' have started swearing blood oaths that are magically binding, resulting in DeathOfAThousandCuts if they violate those oaths (particularly the oath of secrecy).

* ''Film/{{If}}'': The three main protagonists Travis, Wallace and Yardley make an oath in this way.

* In ''Anime/MobileSuitZetaGundam'', Paptimus Scirroco seals his loyalty to the Admiral Jamitov Hymen and Titans with a bloody thumbprint. [[spoiler: This does not stop him from murdering Jamitov and taking over the organization.]]

** An interesting variation occurs as Naruto swears to Neji on ''Hinata's'' blood during the Chunin exam preliminary battles for the final test, "You... are going down", promising to defeat him. He makes the same gesture at the beginning of their fight in the finals.

* In ''Film/CurseOfTheCrimsonAltar'', Peter signs Lavinia's book in blood. According to Professor Walsh, this is a step there is no coming back from.

[[folder:Anime and Manga]]
* It's implied that this is the traditional way in ''Manga/NegimaMagisterNegiMagi'' to induce a Pactio. But that's messy and doesn't have nearly enough fanservice, so they kiss instead.
* This is also all one really has to do to exchange mana in the Franchise/{{Nasuverse}} as well. Again, sex is more fanservice.

* In ''Anime/MobileSuitZetaGundam'', Paptimus Scirroco seals his loyalty to the Admiral Jamitov Hymen and Titans with a bloody thumbprint. [[spoiler: This does not stop him from murdering Jamitov and taking over the organization.]]
* 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.

* In ''Fanfic/CoventinasCrown'', Morain cuts her palm, lets the blood drip onto fire, and swears by her own blood to bring her kidnapped brother back.

* ''Film/RobinHoodPrinceOfThieves'': Kevin Costner's Robin Hood does it when he swears to avenge his father's death.
* The wild men swear to obey Saruman this way in ''Film/TheLordOfTheRings''.

* ''Film/TheOutlawJoseyWales'' and Ten Bears take a blood oath to seal the "words of iron" peace treaty between the Comanches and Josey's friends at the Turner Ranch and Santo Rio. It is strongly implied, though unstated, that this also makes Josey and Ten Bears BloodBrothers.

* ''Film/FaustLoveOfTheDamned'': Jaspers' contract with M for demonic superpowers is, of course, written in blood.
* In ''Film/JohnWickChapter2'', the concept of "Markers" is introduced. When made, the participants are given a special medallion that can be imprinted on with two thumbprints in blood; the person asking for the initial favor must place their thumbprint while the helper hangs on the medallion until it comes time to repay the favor. Once the favor has been repaid, the helper adds their thumbprint and also signs a special book at a their nearest Continental to clear the debt. [[spoiler: John is revealed to have used one of these to help in his "impossible task" when he initially tried to retire, in this film- the crime lord who he asked for help decides that it's time for John to repay the favor, kickstarting the film's central events.]]
* In ''Film/CurseOfTheCrimsonAltar'', Peter signs Lavinia's book in blood. According to Professor Walsh, this is a step there is no coming back from.
* ''Film/PhantomOfTheParadise'': Anyone "under contract" in this movie is implied to have signed one, and we see Winslow sign one onscreen.
-->'''Swan:''' Ink isn't worth anything to me, Winslow.
* ''Film/FantasticBeastsTheCrimesOfGrindelwald'' reveals that Grindelwald and Dumbledore made a blood pact to never fight each other, which is why Dumbledore has made no moves to directly oppose Grindelwald.
* ''Film/TheNest'': Goyita and Alejandro pledge eternal love for each other, when she carves an A on her palm, he carves a G on his, and they clasp hands. This is creepy, because he is 60 and she is 13.
* ''Film/{{If}}'': The three main protagonists Travis, Wallace and Yardley make an oath in this way.

* Tom and Huck do this in ''Literature/TheAdventuresOfTomSawyer'' after witnessing the murder of Dr. Robinson by Injun Joe, vowing to keep it a secret. Notably, they take at least a bit more care with it than in most examples, as Tom insists on using a needle instead of the brass pin Huck offers to eliminate the possibility of blood poisoning by "verdigrease."

* Creator/WhiteWolf:
** ''TabletopGame/VampireTheRequiem'' has the Invictus (a covenant of fedualist vampires heavy on inherited power) and their Blood Oaths, magical bonds with ''heavy'' penalties for violation.
** ''TabletopGame/ChangelingTheLost'' has many forms of oaths, and your health or life can be put on the line for them. With heavy costs comes heavy rewards - the more you'll lose if you break the oath, the more benefit you can gain from it.
* The card [[http://gatherer.wizards.com/Pages/Card/Details.aspx?multiverseid=205118 Sign in Blood]] from ''TabletopGame/MagicTheGathering''. Apparently it's quite a long document, because it hurts as much as getting mauled by a bear.
* Starting with 4th Edition, some of the Triad gangs in ''Tabletopgame/{{Shadowrun}}'' have started swearing blood oaths that are magically binding, resulting in DeathOfAThousandCuts if they violate those oaths (particularly the oath of secrecy).

* A quest chain in ''VideoGame/WorldOfWarcraft'' starts off with you making one of these with a troll, to show that you'll both honor a truce. He honors it, in that he [[spoiler:never does anything to harm ''you'', specifically, although you're tricked into doing horrible things.]]
** In the backstory, the original Orc chieftains on Draenor gave themselves up willingly to the Burning Legion for power. To seal the pact, the chieftains drank the blood of Mannoroth, binding the entire Orc race to him while infusing them with his fell power.

* Okku from ''VideoGame/NeverwinterNights2: Mask of the Betrayer'' swears in blood to stop the recently emerged spirit-eater (that is, you, the protagonist). If spared, he calls a truce which lasts as long as you agree to suppress your urge to devour spirits and breaks if you meet certain conditions (commiting some certain evil acts in Okku's presence or getting his approval below zero).
* ''VideoGame/GodOfWarI'': "Ares! Destroy my enemies and my life is yours!" ''[[VideoGame/GodOfWarAscension Ascension]]'' reveals that this was a Blood Oath. Kratos spilled the blood of his enemies, the blood of the innocent, and the blood of his family. When Kratos turned against Ares after that last one, the Furies hounded him to bring him back to Ares' service.

* Madoc of ''Webcomic/WakeTheSleepers'' accepts a contract through blood on a bounty, as his crazy Assassin culture requires.

* In ''Webcomic/BadMachinery'' Erin Winters demands that contracts acknowledging people owe her a favor be signed in blood. Given that the last time she was seen in ''Webcomic/ScaryGoRound'' before reappearing without explanation in ''Bad Machinery'' she was in the company of and (technically) married to Aleister Crowley, and ''trapped in Hell'', this may bode ill.
* Vard, Kai and Marya are bound to the Unknown Champion with one for a year in exchange for [[spoiler:her]] help saving the woods near where Kai and Marya live in ''Webcomic/UnknownLands''.

* In ''Webcomic/{{Sinfest}}'', [[http://www.sinfest.net/archive_page.php?comicID=3 Satan wants the forms and waiver filled out in blood, of course.]]

* It's implied that this is the traditional way in ''Manga/MahouSenseiNegima'' to induce a Pactio. But that's messy and doesn't have nearly enough fanservice, so they kiss instead.
* This is also all one really has to do to exchange mana in the Franchise/NasuVerse as well. Again, sex is more fanservice.

* ''FanFic/AGrowingAffection'' has the Blood Oath Jutsu, the user swears an oath, sets a condition for breaking said oath (two examples in the story are memory loss and death), and then writes the kanji for ''Honor'' over his or her heart in his or her blood. Breaking the oath will cause the condition to occur. Only one person in the world has ever successfully removed a Blood Oath seal, and she has less than a fifty percent success rate in doing so.

* In ''[[VideoGame/FireEmblemRadiantDawn Fire Emblem: Radiant Dawn]]'', a blood pact is a contract that two or more people sign in blood. If the terms of the pact are not upheld, the person's subjects die off--first slowly, then progressively faster [[spoiler:hence the plague that struck years ago]]. They can only be broken by [[spoiler:killing at least one person involved in the pact AND destroying the document]].
* In ''VideoGame/{{Thief}} 2'' {{Enemy Mine}}s seal their alliance this way (blood on earth variant).
* Okku from ''VideoGame/{{Neverwinter Nights 2}}: Mask of the Betrayer'' swears in blood to stop the recently emerged spirit-eater (that is, you, the protagonist). If spared, he calls a truce which lasts as long as you agree to suppress your urge to devour spirits and breaks if you meet certain conditions (commiting some certain evil acts in Okku's presence or getting his approval below zero).
* [[VideoGame/GodOfWarI "Ares! Destroy my enemies and my life is yours!"]] ''[[VideoGame/GodOfWarAscension Ascension]]'' reveals that this was a Blood Oath. Kratos spilled the blood of his enemies, the blood of the innocent, and the blood of his family. When Kratos turned against Ares after that last one, the Furies hounded him to bring him back to Ares' service.

* Tom and Huck do this in ''Literature/TheAdventuresOfTomSawyer'' after witnessing the murder of Dr. Robinson by Injun Joe. Notably, they take at least a bit more care with it than in most examples, as Tom insists on using a needle instead of the brass pin Huck offers to eliminate the possibility of blood poisoning by "verdigrease."

* A blood oath has a hand in setting up the plot of ''[[FanFic/AngelOfTheBat Angel of the Bat: Da Pacem Domine]]'', with the added bonus that it is magical in nature. ComicBook/JohnConstantine is bound by an oath to {{ComicBook/Azrael}} to deliver a message in his stead should he be killed in the line of duty. Attempting to leak the secret to anyone but its designated target causes Constantine to cough and choke, drowning out the message.

->"Hey, she's got to. She's signed a contract. It's all down in red and white!"
-->-- B.L. Zebub, ''WesternAnimation/TheDevilAndDanielMouse''

* In ''TabletopGame/{{Earthdawn}}'', magical blood charms are used to seal bargains: if either person violates the conditions, the magic punishes the violator.

* In ''Fanfic/CoventinasCrown'', Morain cuts her palm, lets the blood drip onto fire, and swears by her own blood to bring her kidnappex brother back.

* The 1876 April Uprising, UsefulNotes/{{Bulgaria}}'s most significant rebellion against the Ottoman Empire, was declared through the so-called "Blood Letter", which the RebelLeader Todor Kableshkov signed with the blood of his hometown's murdered governor and sent to the town where [[LaResistance the revolutionary organisation]]'s HQ resided.

* In one episode of ''WesternAnimation/ThePowerPuffGirls2016,'' Bubbles and Buttercup sell Blossom's soul to HIM for a dollar, and this trope in implied when the girls sign the contract that HIM gives them.

* In one episode of ''WesternAnimation/ThePowerPuffGirls2016,'' Bubbles and Buttercup sell Blossom's soul to HIM for a dollar, and this trope in implied when the girls sign the contract and HIM gives them.

[[folder:Real Life]]
* There are blood vial pendants for sale around the Internet. The idea behind them is for the couple to carry a bit of each other's blood close to their chests as a sign of their bond.