There are three theories about their origin:
- One drop of blood of an Immortal fell down to the Mortal Emperor World and turned into Blood Forefather that ended up giving birth to the entire Blood Race.
- The Blood Race's ancestors were a group of evil creatures hiding in the darkness, monsters that relied on siphoning blood to survive. The master among these evil creatures got together with a woman and their offspring eventually came to be the new Blood Race. This new Blood Race went to war with their ancestors and replaced them completely.
- The Blood Race's progenitor was a devil, he mated with a female corpse, and produced the Race.
The majority of the Blood Race accepted the first legend. They considered themselves to be pure and righteous and naturally, they would deny the second and third legends. At the very least, the Blood Race members located at the Barren Earth believed that these two legends were fabricated by the other races to discredit their clan.
The Blood Primal Ground, the first branch of the Blood Race, as well as several other tribes of their Race exist in the Barren Earth region, but even so they are rarely seen in the Mortal Emperor World.