Black Star

Black Star (ブラックスター, Burakku Stā) is the term used to describe entities who fight Stagnant Souls in the Threshold.

Description
For unexplained reasons, all Black Stars take the form of human girls, and they almost always feature a white star somewhere on their garments. In combat they emit a flame on one of their eyes, and use weapons that are transformed from their non-humanoid partners' bodies.

Black Stars are created from former Stagnant Souls by removing their consciousness and memories, making them more or less emotionless and obedient puppets. However, in some rare cases they may regain emotions and individuality. Should such Black Stars then fall into despair, however, they may regress into Stagnant Souls.

Stagnant Souls vastly outnumber Black Stars; there are approximately two million Black Stars available against one hundred million Stagnant Souls by the time Rock is dispatched with Acta to retrieve a tiger's soul. According to Jiou, who simply regards Black Stars as expendable pawns, states that they are prone to spoil if they are not put into good use, implying a limited life expectancy even outside of combat.

Ram states she is the first Black Star, and it is her idea to create Black Stars from Stagnant Souls in order to have them fight each other. However, when she realizes that the Threshold does not undergo any changes despite her meddling, she claims that the conception of Black Stars has been a completely pointless experiment.