

Shiki is called the "greatest singularity", as he directly identifies her as Sion despite his memory of the previous TATARI incident being sealed. Interactions with Shiki and Riesbyfe bring about her true emotions, and surface the will of Sion that wishes for the destruction of TATARI and the prevention of the birth of an even superior TATARI. Osiris can understand Sion's jealousy of Akiha's ability to decide based on her emotions. Akiha claims that even if they're the same person Dust of Osiris is simply not the Sion she knows, and Osiris agrees that while she and Sion are both in ruin, it is Sion who is alive. The original will of Sion still exists within Osiris, and she feels troubled facing her own "worst possible condition" of Sion TATARI having embraced her vampirism. Sion TATARI likewise says that she would have reached the same conclusion as Osiris had she stayed at Atlas, but she thinks Osiris is foolish for only being able to come up with an ending that boring even though she was able to create the Philosopher's Stones. Sion says that indeed originally this would have been her goal, but she has changed since three years ago and now believes in a better future, which surprises Osiris. She believes she is the discarded human husk of Sion that was taken in by TATARI, and later developed into the "giant of Atlas", who differs from the vampiric remains of the real Sion who "degenerated towards humanity" and Sion TATARI who "degenerated into a demon." She believes the original Sion also seeks the same conclusion, as they split from the same person.

When Dust of Osiris is defeated, she briefly takes the form of Sion before disappearing. Osiris claims to lack emotions and ego, believing them to be what destroyed humanity, generally referring to everything with specific calculations, recalculations, and possible mental burdens as "processing slowdown." She only speaks to certain individuals that she encounters, and otherwise she simply continues with her calculations in a robotic fashion while preparing to destroy the intrusion. She believes that this is the "final and ultimate method of salvation" due to the fact that the self-destruction of humanity is unavoidable. She is brought forth one year after the Night of Wallachia was destroyed by Arcueid Brunestud and Shiki Tohno, and uses her abilities to recreate the events of the previous year, "Hologram Summer", once again in an attempt to form an even superior "Night of Wallachia." Her goal is to reach the future summoned by Arcueid to defeat Wallachia. Having found no way to save humanity, much like Zepia hundreds of years beforehand, she was eventually appointed as one of the Twenty Seven after Wallachia's death and sought to protect the future by destroying it herself and keeping an eternal record.

She worked on creating the Philosopher's Stone to cure vampirism and revive Riesbyfe Stridberg, and also continued acting as an Eltnam while working on the prediction of the future for the purpose of protecting humanity from unavoidable destruction and the acquisition of a method of salvation from it. She is a potential future version of Sion should she stay with Atlas rather than chase Wallachia to Japan and eventually reach the position of chief of Atlas. Normally it would have been an impossible struggle, but when Night of Wallachia was destroyed she was able to take control of TATARI. The pieces of her soul developed correctly within TATARI over time and fought to seize TATARI's control system. Dust of Osiris is a version of Sion created from remnants of her soul consumed by Wallachia after drinking three liters of her blood.
