Chaos
Chaos is the primordial force trapped in the Galaxy Cauldron—basically a massive void of black fourth-dimensional space. It's the real villain behind Sailor Moon's entire saga. Rather than act directly, Chaos sends out incarnations that become her major enemies: Queen Metaria, Death Phantom, Pharaoh 90, and Queen Nehellenia. Eventually it manipulates Sailor Galaxia into stealing Sailor Crystals so it can break free and take over the galaxy.
When Sailor Moon finally defeats it, she forces Chaos back into the Galaxy Cauldron. Everyone who died in the conflict gets sent back to their home planets and times, reincarnated after the battle. But here's the catch—Chaos doesn't actually die. It's destined to be reborn.
Sailor Chaos
In the manga's distant future, Chaos emerges from the Galaxy Cauldron as Sailor Chaos, a powerful Senshi in its own right. Sailor Cosmos, exhausted from an endless cycle of battles against this evolved form, disguises herself as Chibichibi and travels back in time to convince Sailor Moon to destroy the Galaxy Cauldron entirely, preventing Chaos's rebirth and the wars that would follow.
In the anime, Sailor Chaos never actually appears. Chaos itself shows up only briefly in episode 200, getting expelled from Galaxia's body after her defeat. The story resolves differently there: Galaxia reveals she sealed Chaos inside herself long ago to save the galaxy. She was being controlled by it, but Usagi reaches the hope still buried in Galaxia's heart, allowing her to release Chaos and end the threat.
Content compiled by AnimeList.moe from publicly available sources.
