A Blood Breed is a powerful creature from the Alterworld. Blood Breeds are some of the strongest antagonists in the series, able to give Libra considerable trouble in battle. In contrast to the average creature from the Alterworld, Blood Breeds are quite savage and bloodthirsty.
An upper-class subset called the Elder Blood Breeds also exist, which are generally more dangerous than the average Blood Breed. Originally thought by Libra to only number thirteen, Leonardo Watch's Eyes of God showed that the true number of Elder Blood Breeds was far more numerous.
Blood Breeds possess immense strength, speed, and destructive capacity, as well as an identifiable crimson aura. Two Blood Breeds shown thus far have been able to manipulate their blood into objects to attack and turn living beings into obedient ghouls. Blood Breeds cannot be seen through the naked eye, although the Eyes of God are capable of detecting a Blood Breed even through other devices, such as cameras or mirrors, are able to see its true name if its heart is present in the relevant body.
Blood Breeds are also capable of regeneration; Elder Blood Breeds are even more skilled in that regard and may even be able to control parts of their body that have been split off from the whole: Girika was able to regenerate from the combined attacks of Steven A. Starphase and K.K. casually even after K.K.'s shot took off a significant portion of her head. Herlelle was fighting Raju Jugei Shizuyoshi with his lower body alone, and even that lower body was able to resist the latter's conjured fire storm for some time.
Even then, this did not yield in his end, as it encased itself in a Zhen Tai Dan (Chinese for "true womb egg"), a multi-eyed egg that defends the Blood Breed or its significant body parts and attacks those that get close enough to it while the Blood Breed regenerates within the egg. A tentacle from the Zhen Tai Dan of Herlelle's lower body was able to casually deflect bullets from a semi-automatic gun held by an armored police officer, and then tear apart the armored arm holding the gun, and even attack Zapp before he was able to conjure up his Blade 1: Homuramaru.
- Count Urthrchika (Manga Only)
- Valsh Rozzo Valctovoel Girika
- Tonio Andretti is a lower-class Blood Breed, having become one not long after Girika's intervention. Due to his relatively fresh vampirism, he is insufficient to combat a squad of armored police officers alone, requiring his mistress's help to do so. He attempts to intervene after Klaus leaps out of the subway to attack the pair, but is quickly crushed by Klaus's attack.
- Herlelle Lucando Lozo Thietkaua gi Murmhavat
- An unnamed Blood Breed appeared as a blood construct that exploded from Ozmaldo after his fight with Klaus Von Reinherz. This Blood Breed was able to effortlessly punch Klaus into the wall of the cage the two had fought in. As Klaus still had the energy to beat down Zapp Renfro even after that fight, it is implied that this Blood Breed was eventually destroyed or sealed.
- A Blood Breed might be considered equivalent to our world's mythologized vampires.