The Blood Curse (血脉诅咒, Xuèmài zǔzhòu) is a curse in the blood of those born in Miraland that prevents them from resorting to force. After using force, a person affected by the Blood Curse will be overcome by burning pain in their heart.
The Blood Curse is at least in part guided by the intention behind the act. Because of this, whether somebody suffers from the backlash of the Blood Curse is used in court to determine if they are guilty.
The Blood Curse began in this year, following the assassination of a man who went by the name The Enlightened. He attempted to bring about peace to Miraland, and for the decade preceding his assassination, all production of military technology and use of weaponry was forbidden. However, this period, known as the "Golden Decade", ended when he was killed.
When the curse began, cruelty and chaos were stopped, and wars were prevented. However, despite the supposed peace and the new era of "light", some view the security provided by the Blood Curse as only a mirage. It's implied that in some way, the Enlightened himself began the Blood Curse, as an old poem describing the event writes that "vengeance burns painfully" after his death.
It's said that the Nameless Chivalric Order guards the key that holds a clue to breaking the Blood Curse.  Despite their best efforts to protect the key, in the year 677 it was nearly stolen from their fortress by a rogue pharmacist from Losol named Morrison (known also as Gray Raven).
There is a reagent that is able to completely reduce the backlash from the Blood Curse. It is considered top-secret, and for many years it was only available to the elites of Black Water City. It was administered to entire armies in order to ensure their victory.
Morrison created a reagent that shared the same properties, or possibly just renamed the one from before, and called it No. 7 Reagent. Though it will suppress the pain, the reagent is a poison that results in a myriad of other side effects.
The reagent is administered through a syringe. Taking the reagent can, at the very least, cause the drinker to see stars, experience dizziness, and lose track of time, though it's remarked by Peachy that these are only the most normal side effects.
Shade was created around or before the year 677, using the body of a deceased Apple Federation soldier named Flynn, in order to "transcend" the Blood Curse. Though the curse still applies to him, he cannot feel physical pain, meaning that he does not suffer from its effects.
In a world governed by the Blood Curse, there are many conflicting opinions on it.
Regent Bai Yongxi believes that the Cloud Empire thrives under the peace and prosperity of the Blood Curse. Due to their vulnerable geographic position and lack of significant military force, he believes that if the curse were to disappear, the empire would fall. However, South King Zhu Yuxian believes that the curse only provides a veil of peace and that war is too inevitable for them to ignore it. He believes that those who protect the country should not have to face the curse.
Colonel Nidhogg, a native of the North Kingdom, believes that the Blood Curse also brings a false peace. He believes that those who seek peace, such as Louie, are idealistic and that true peace does not exist at all.
This belief stems from an incident when he was serving as a knight of the Knight of Kingdom, the soldiers that serve the king of North Kingdom. When he, Louie, and Louie's father the Knight Commander were sleeping, a group of soldiers attacked who used the reagent to fight without the pain of the Blood Curse. With one side completely invincible against the Blood Curse and Nidhogg's side suffering from the backlash, their loss was swift. The Knight Commander eventually met his death not at the fate of another soldier, but rather from the backlash of the Blood Curse overcoming him.
Nidhogg felt that this potion made the rule of the Blood Curse unfair: when war would inevitably break out, the curse punished those that adhered to it, rather than those who broke it by using the reagent. Years later, Nidhogg refused to take the reagent that would suppress the pain of the Blood Curse.
The following people all suffered from the Blood Curse.
|Nidhogg, Louie, Louie's Father, Ray, other soldiers||They fought back against attackers in their camp who were immune to the Blood Curse. Louie's father was so overcome by the backlash of the curse that he died.||670||Sea of Trees, Ice Abyss Echo, Ashen Glory|
|Soldier||He fought in the Nine-Day War.||672||Peace Prayer|
|Strange Man||He kicked Bobo's father, then fatally shot him with a gun. He claimed not to care about the Blood Curse.||677||Bobo's Dreamland, Parting in the Snow, Black Bullet|
|Nidhogg||He fatally stabbed Lunar through the midsection.||680||V1: 15-9 Compete with Nidhogg|
|Zhu Yuxian||He stabbed Ming Shuiyuan through the midsection. However, it was indicated that he hardly felt the Blood Curse compared to a suffocating feeling, possibly related to his suppressed memories.||680||Ming Shuiyuan's Dreamland Moon Reflection, Final Farewell|
|Lord's Soldiers||They attempted to fight off Royce in order to gain access to something in the royal treasury.||680||Sea of Trees Event Story, Black White Puzzle, Oath of Accompany|
|Nicolas||He killed a man. He told police it was an accident so he was not given anesthetics to reduce the pain. However, during the trial, he was overcome by the pain of the curse.||680||Night Prelude/War Report - Manuscript No.803|
It is likely that these people suffered from the Blood Curse due to using force; however, it was never outright stated.
|Neva||She stabbed many soldiers after seeing the Blood Moon in the sky.||circa 669||Sea of Trees Event Story, Black White Puzzle|
|Viper Leader||He fatally shot Flynn with a poisonous bullet from a gun.||670||Orlando's Dreamland, Immortal Glory, Hidden Scenery|
|Orlando||He fatally shot the Viper Leader with an electromagnetic gun disguised as an umbrella.||670||Orlando's Dreamland, Immortal Glory, Immortal Glory|
|Lionel||He critically injured Gray Raven by throwing a spear in him.||677||Louie's Dreamland, Nameless Knight, Battle in Deep Snow|
|Lu Yinian||She fought off people who were trying to kidnap Nikki.||680||V1: 7-8 Lu Yinian, the Heroine|
|Yue Qianshuang||She and her army fought against the forces of Zhu Yuxian, with Yue Qianshuang using a sword.
Note: Zhu Yuxian does say at another point in the story that soldiers suffer from the curse; however, it is not mentioned at this time.
|680||Art of War Event Story, Cloud in Flames|
|Xiao Zong||He killed a soldier with a sword.
Note: At the time, Xiao Zong was also said to be drunk.
|680||Art of War Event Story, Misty Peaks|
|Aten||She shot a man with a gun.||Unknown||Feast of Hunt|