|Although this article is based on canonical information, the actual name of this subject is conjectural.|
- "- Herein lies your truest strength.
- The energy of the Demon. Its spirit.
- Its heart.
-This is how you...
- Created the First Slayer? Yes."
- ―The Shadow Men and Buffy Summers[src]
The demon's exact origins are unknown. At some point in the past, it had been captured and controlled by the Shadow Men, who would use it to create the First Slayer.
The Era of Sineya
The Shadow Men chose a girl named Sineya to contain the power of the demon. They chained Sineya to the ground so that she could neither defend herself nor escape, then unleashed the demon, which appeared to be in the form of dark black energy vapors. It forcibly merged itself with Sineya, granting her superhuman strength, speed, reflexes, agility, superior healing factor, a predator instinct, innately formidable combat techniques and quite possibly some kind of advanced prophetic ability. However, the process also caused the First Slayer to lose touch with her own humanity forever. Future Slayers were able to retain their humanity, but not have as much power as the First Slayer.
War Against the First
Thousands of years later, the Shadow Men tried to repeat history with Buffy Summers in order to empower her even more so she would be able to defeat the Turok-Han army of the First Evil. However, Buffy sought knowledge, not power, especially if that power meant that she would lose her humanity. She repeatedly denied the entry of the demon into her, forcing it and keeping it out. Buffy then broke free from her chains to stop the Shadow Men, thus effectively incapacitating the shadow demon.
After she was shown the Turok-Han army, however, Buffy had doubts on whether she should have accepted the increased strength that the demon would have given her. Later on, through the scythe, Willow divided the power of the Slayer with each and every Potential in the world, which ended the original lineage of Slayers.
Powers and abilities
- Power Bestowal: Upon being merged with Sineya, the shadow demon granted her all the powers associated with a Slayer, so it is highly likely that it possessed those powers as well. Through the magic of the Shadow Men, subsequent Slayers were also granted the same powers, though not as potent as the First Slayer's.
- Power Augmentation: As seen by how the Shadow Men tried to merge the demon with Buffy to empower her to defeat the Turok-Han army, the demon had the ability to enhance the power of a Slayer to the extent where she could reach a level that was usually beyond her limit.