Chaos

Because it spends the greater part of the season inhabiting Sailor Galaxia, the entity keeps its own shape hidden from view. Only when Sailor Moon drives it out of the warrior's body does its real form flash into sight, a living clot of jet-black energy. Should it seize Galaxia entirely, the two fuse into a grimmer, mightier incarnation called Chaos Galaxia, a near-mirror of the original but with every gilded piece of the uniform turned black, the hair dyed blood-red, the skin gone grey, and a set of large bat-like wings sprouting for flight. The Sailor Stars opening, meanwhile, pictures it as something closer to a human silhouette with tapered ears, flowing hair, and burning red eyes, its whole body woven from crimson and dark blue energy.

What makes this villain unlike any before it is the absence of scheme or motive. Earlier foes acted on grudges, ambitions, or elaborate designs, yet Chaos wills nothing at all. It is a slumbering evil that stirs wickedness inside whoever tries to wipe it out, an evil that cannot be erased from the world for as long as people exist. Even so, in its Chaos Galaxia guise it set about harvesting star seeds and, in effect, snuffing out all human life in a bid to command the universe.

In this continuity Galaxia once managed to imprison Chaos, only for it to gradually corrupt her from within. Before she fell completely, she launched her own Star Seed, the Light of Hope, into the void with orders to seek out the stars of love and justice. That seed eventually reached Sailor Moon and adopted a shape mirroring her, appearing as the child Chibi Chibi. The struggle ends when Princess Serenity frees Galaxia on her own and forces Chaos out of that powerful body, telling her that the darkness must never be fought in isolation but instead held a little within every human heart, where it can never take full hold.