Nightblood

Nightblood is a genetic trait that makes people resistant to radiation but also makes their blood black. People with nightblood are also known as "Nightbloods" or Natblida (in Trigedasleng) among the Grounders. Nightblood was genetically engineered by Becca Franco to increase people's resistance to radiation. It can be inherited but it is hereditarily rare; and the few who inherit it are often treated as special or royals. Among the Grounders, nightblood was considered to be the blood of the Commander and only Nightbloods were allowed to become commanders.

In Sanctum, it is considered Royal Blood, and those with the royal blood eventually become the "Hosts" for the Primes. It is also referred to as Black Blood.

Becca Franco created the Nightblood serum for the Eligius Corporation to increase their resistance to radiation. The serum was successful but had an additional consequence of making the subject's blood become black. It genetically altered the subject, making the condition hereditary. However, the condition is recessive, causing it often to skip generations. According to Russell Lightbourne, Nightbloods won't be born for 56 years, until they're born.

Nightblood is important in both Grounder and Sanctum culture. For Grounders, only Nightbloods can become Commanders as they are the only ones compatible with the Flame. In Sanctum, Nightbloods are believed to be the hosts of the Primes.

History
Two years after the Nuclear Apocalypse, Becca injected herself with a black substance, i.e. Nightblood serum, that genetically modified her blood, turning it black. This modification allowed her to metabolize radiation at a much higher rate, including the radiation emitted by A.L.I.E. 2.0, solar radiation, and remaining nuclear radiation on Earth. Afterwards, Becca implanted A.L.I.E. 2.0 into her neck. When Becca returned to Earth, she saw humans in hazmat suits in the distance and told them that she was there to help, and brought a case full of Nightblood serum in tow. According to Titus, the people became the first Nightbloods.

Becca's tale became the origin story of the First Commander, (Pramheda[Trigedasleng]) and those with the dark blood became known as Nightbloods (Natblida[Trigedasleng]). The majority of Grounders have normal colored blood, but may be carriers for the dark blood since Nightblood children can be born to non-Nightblood parents. Whoever is the current bearer of A.L.I.E. 2.0 becomes known as the Commander (Heda in Trigedasleng).

While Grounders lost most of the knowledge on what the dark blood does, in the fourth season, Abigail Griffin discovers that its sole purpose is to metabolize radiation. She notices this when Luna, a Nightblood, was able to fully recover from Acute Radiation Syndrome (ARS) without any medicine, while non-Nightblood Grounders died from it.

Throughout the Series
In Stealing Fire, after Commander Lexa is accidentally killed by Titus, Ontari slaughters the other Nightbloods in Polis in their sleep before the Conclave, and presents their heads in the throne room to declare her victory.

In Perverse Instantiation (Part 2), Clarke, with Abby's help, utilized an exchange transfusion, similar to the ones done at Mount Weather, to replace her blood with Ontari's. This transfusion allowed Clarke to temporarily become a Nightblood and accept the Flame. However, it was only successful so long as Ontari's blood continued to circulate through Clarke's body, requiring Abby to open Ontari's chest so that Murphy could manually pump her heart and keep it beating when Clarke's condition deteriorated.

During the fourth season, after her Nightblood made Luna immune to the radiation of the second apocalypse, an attempt was made to recreate Nightblood to survive the coming death wave. Eventually, Clarke was given Nightblood via a bone marrow transplant from Luna, but due to Abby's fears for her daughter, the Nightblood went untested. In The Chosen, Clarke was exposed to radiation and later became sick, but it was theorized from Luna's experience that it may take a few days for the Nightblood resistance to kick in. In Praimfaya, Clarke's Nightblood succeeds in saving her from the death wave with a young Nightblood named Madi surviving as well.

In The Children of Gabriel, Russell reveals that on Sanctum, nightblood is the blood of royalty, and he refers to it as the 'royal blood'.

Conclave
The Conclave is Grounder tradition, held upon the death of the Commander in which a Nightblood successor for the role is selected. The Flamekeeper (or Fleimkepa in Trigedasleng) is responsible for retrieval of the Flame from the previous Commander's corpse and overseeing the Conclave for the selection of the new Commander.

The Flamekeeper uses scouts to find Nightbloods. When a Nightblood child is discovered, they are sent to Polis to begin training for their Conclave. For each group, or "class", of novitiates, a Conclave is held when the last Commander dies, during which the Nightbloods fight to the death. The survivor then becomes, or, "ascends" as the next Commander. The belief among Grounders is that the Commander's spirit (in fact the A.I. chip of A.L.I.E. 2.0) "chooses" its successor through this process.

Once the victory horn is sounded, the victor is taken to the throne room, where the Flamekeeper performs the Ascension Ceremony in which the victorious Nightblood becomes the Commander. The Flame from the old Commander is implanted into the neck of its new successor, and with it, the new Commander is endowed with the spirits of all the past Commanders. As part of the rites of Ascension for a new Commander, they are required to recite the lineage of past Commanders. If they are incapable of doing so, they are considered illegitimate.

Notable Nightbloods

 * Becca Franco, the first Commander.
 * Commanders who ruled after Becca and before Lexa and members of their Conclaves. At least four, during the time of Flamekeeper Titus.
 * Lexa's Conclave: Lexa, Luna, Luna's brother and six other novitiates.
 * Ontari's Conclave: Ontari, Aden and six other novitiates.
 * Clarke Griffin
 * Madi Griffin
 * Kaylee
 * Russell Lightbourne
 * Simone Lightbourne
 * Josephine Lightbourne
 * Gabriel Santiago
 * Delilah Workman
 * Priya Desai
 * Ryker Desai
 * Rose
 * Miranda
 * Other Sanctum Primes

Nightblood (Serum)
"Nightblood" is also used to refer to an experimental serum created by Becca. According to the records, she first developed it for the Eligius Mining Company to protect against solar radiation for long duration space missions. She later used the serum to help the human body not reject the A.L.I.E. 2.0, protecting the body against radiation emitted from the device. In addition, it also helps the human body metabolize nuclear radiation. Becca made the cells combine by experimenting in space with perfluorochemicals and oxygenators, the building block of artificial blood.

Notes and Trivia

 * Past Commanders are honored on Ascension Day.
 * The Flame is passed from commander to commander. When a commander dies, the Flamekeeper takes the Flame from the dead regent and guards it until the Conclave is over and the next commander has been revealed.
 * If the Commander dies in battle, the Flamekeeper or one of their scouts would have been tasked with finding the commander's body and retrieving the Flame.
 * The Flame will bond with anyone who has nightblood. Anyone who doesn't have Nightblood and comes into contact with the Flame will die.
 * If a Nightblood flees or refuses to participate in the Conclave, they are considered cowards and traitors to the blood and are typically hunted down. As was in the case of Luna.
 * Nightbloods were first revealed in Watch the Thrones. Following Clarke's failed assassination of Nia, Nia drips Ontari's blood onto Clarke's face explaining that Ontari will become the next commander. When Clarke asks Lexa about the nightblood, she explains it is the blood of the commanders.
 * Becca first developed Nightblood for the Eligius Corporation for them to use on prisoners and colonists, who were spending prolonged periods of time in space and needed protection from radiation.
 * In Sleeping Giants, Miles Shaw reveals that the spaceship called, Eligius III, had Nightbloods.
 * The Nightblood resistance does not kick in right away as seen with Luna and Clarke Griffin. Both got sick for a few days after being exposed to radiation before their Nightblood cured them. Clarke originally thought that her Nightblood had failed before Bellamy Blake pointed out the time delay with Luna's resistance.

Gallery

 * -|Nightbloods=