In the manga, Chaos is the ultimate expression of nothingness and source of darkness. It has caused many of the battles fought by the Sailor Senshi, and is the strongest villain Sailor Moon ever faces.
Chaos was responsible for seducing Sailor Galaxia with promises of powers. It is also revealed that all of the primary antagonists (Queen Metaria, Death Phantom, Pharaoh 90 and Queen Nehellenia) were incarnations of Chaos.
Chaos refers to itself as one who never became a star. It exists as the ultimate expression of nothingness and its goal to once again become one with everything in the universe.
When Sailor Moon reaches the Galaxy Cauldron, she discovers that Chaos and Sailor Cosmos urged Sailor Moon to destroy the Galaxy Cauldron, which would prevent Chaos from returning to torment the galaxy, but would prevent new stars from being born. Sailor Moon refused to destroy it and plunged into the Cauldron, taking Chaos with her, which destroyed Chaos.
Chaos woud return someday, but for the time being, the galaxy gained a reprieve from Chaos' influence.
Chaos' personality is very vague to describe, as it seems to be very emotionless and without much care for what it does to Sailor Moon.
Chaos is an immortal being, and so long as the Galaxy Cauldron exists, it will never die permanently. And through some vague degree, it is responsible for the existence of the other antagonists that Sailor Moon had to fight.
- Chaos is named after Chaos from Greek mythology. Chaos was a primordial god, a dark shapeless void, and the original state of existence from which the first entities appeared. The mythological Chaos was neither good nor evil, and was rather just the ultimate expression of nothingness and the uncaring creator of the cosmos.