The Kaleid Blood or Kaleid Bloodline is an artificial bloodline created by the three primogenitors as the strongest God-Killing weapon. But it proved to be so powerful that they could not control it, and it eventually turned on them. In the end, they divided the bloodline into twelve parts between twelve vampires that would represent the twelve Beast Vassals.
The Original Fourth Primogenitor was a God-killing weapon created to slay Cain, the Sinful God. In the beginning, he was placed by Cain's side as his observer, and was ordered by his creators, the Devas, to kill him in the event he were to activate the Cleansing (the forbidden God-Killing ritual he created to slay deities by rewriting the information of the world), and use it against them. However the Fourth Primogenitor, having become close to him due to the great amount of time he spent by his side, began to think of Cain as his closest friend. And Cain felt likewise, embracing the friendship between them. The Devas took this outcome into consideration, however, as when they created the Fourth Primogenitor, they intergrated a curse into the artificial soul. It was the curse called Root, an alternate personality that functioned as an autonomous killing program that would surface and possess the Fourth Primogenitor when certain conditions were met. And under the control of the personality of Root, the Fourth Primogenitor killed Cain, and consumed him. Having been forced to slay his only friend, the Fourth Primogenitor fell into dispair and turned on the Devas who created him in the name of revenge. Ironically, Cain's activation of the Cleansing had striped the Devas of their immortality and divinity, making them helpless before onslaught of the Fourth Primogenitor, the strongest God-Killing weapon. And so, the Devas were destroyed. Their civilisation, their technology, all of it was laid waste to, burned to ashes by the wrath of a God-Killing weapon of their own making.
The Fourth Primogenitor was ultimately defeated in the end though, by a small handfull of surviving Devas and the three primogenitors, and was sealed. They split the Fourth Primogenitor's power into twelve parts, using his ribs and blood to create twelve more artificial vampires to serve as hosts for the Fourth Primogenitor's Beast Vassals. However, unlike the Fourth Primogenitor, they where incomplete, having no souls or minds of their own, so when the Beast Vassals where planted into them, they took control of the empty vessels from within, gaining bodies of flesh and blood and minds of their own. These twelve vampires controlled by the Beast Vassals within them where called the Kaleid Blood's, numbering from one to twelve, and where sealed away all over the world. The 12th Kaleid Blood, who would be later named Avrora Florestina, became the host, and living seal of the Fourth Primogenitor's artificial cursed soul, (which by that time had been assimilated by the Root persona), in addition to the 12th Beast Vassal, and was in turn sealed away in the Fairy's Coffin, a temple located on an island in the center of the Mediterranean Sea. She would sleep there for untold millennia, until the tomb was discovered by an research team lead by an archaeologist named Akatsuki Gajou, which would lead to the Akatsuki sibilings encounter with her, an encounter that caused the fates of the three to move.
The Black Death Emperor Front's attack on the temple would lead to Akatsuki Kojou's death, which caused Akatsuki Nagisa to use her abnormally strong power as a spirit mediem to take Root, the Fourth Primogenitor's artificial cursed soul, from Avrora into herself and temporarily control it, using it to forcfully summon the 12th Beast Vassal within Avrora and use it to destroy the terrorist's invading the temple. After this she would have Avrora resurrect her brother by transplanting two of her ribs into him, reviving Kojou as a Blood Servant. Nagisa, on the other hand, fell into a coma due to the strain of housing Root's soul within her body as a mere human. Her condition would inprove somewhat over the next three years after that, but ultimately she was completely possessed by Root when the cursed soul awoke due the activation of the Blazing Banquet on Itogami Island.
As the Blazing Banquet began, Root, having seized Nagisa's body for herself, proceded to devoure the 1st, 2nd, 7th, 8th, 9th and 11th Kaleid Bloods, taking back the parts of herself that had been forcefully ripped away, and attempted to absorb Avrora Florestina, but decided to let her and Kojou flee temporarily, finding their struggle against her to be amusing. Later on, near the end of the Banquet, Kojou and Avrora were joined by the 3rd, 4th, and 5th, Kaleid Blood's, who shared Kojou's desire to save Nagisa, in addition to the 9th, Enatos, who defied Root's control after choosing to stand by Kojou and Avrora, turning on her proper lord and master to fight for their sake (likely because he treated her as a "human", instead of a weapon). The battle came to an end when Avrora devoured Root from within Nagisa, taking the other Kaleid Blood's Root had absorbed into herself and almost completing the Kaleid Bloodline, with only the 6th and the 10th, Kaleid Blood's missing and became a near-complete Fourth Primogenitor. Aurora, knowing that Root would possess her eventually, proceeded to split the Fourth Primogenitor's power away from Root's soul within her, and passed it onto Akatsuki Kojou, granting him the Kaleid Blood's power, legacy, and Blood Memory. She then invoked blood compulsion to force him to use the primogenitor slaying stake he was carrying to kill her alongside Root's soul, robbing him of all his memories of her in the process. He then became the Fourth Primogenitor in her place, inheriting everything that the Kaleid Bloodline entails.
- 0th representative - Kenon
- 1st representative - Prote
- 2nd representative - Deutera
- 3rd representative - Tritos
- 4th representative - Tetartos
- 5th representative - Pemptos
- 6th representative - Hektos
- 7th representative -Evdomos
- 8th representative -Ogdoos
- 9th representative - Enatos
- 10th representative - December (Dekatos)
- 11th representative - Endekatos
- 12th representative - Avrora Florestina (Dodekatos)