Chaos (カオス, Kaosu) was said to be the source of all evil in the galaxy. It is the final villain Sailor Moon had to face.
Quick Answers
What is the true form of Chaos in the anime?
How does Sailor Moon expel Chaos from Galaxia's body?
How does Chaos use Sailor Galaxia's body in the anime?
Who is the final villain Sailor Moon has to face?
What is the role of Chaos in the galaxy according to the anime?
Appearance[]
Since Chaos possesses Sailor Galaxia for a majority of the anime, it's true appearance is mostly concealed. The only time Chaos actually reveals its true form is when Sailor Moon expels Chaos out of Galaxia’s body. In these brief moments, Chaos appears as a sentient mass of pitch black energy.
When it gains complete control over Sailor Galaxia's body, it results in a transformation into a darker and more powerful form known as Chaos Galaxia. This form is very similar to Sailor Galaxia in appearance (who she is the possessed form of), except all of the golden parts of Galaxia's uniform are black. Her hair is a blood-red color, her skin is grey in color, and she has golden eyes with blue eyeliner. In this form, she gains two large bat-like wings, which can be used to fly. She also no longer has her bracelets due to them being shattered upon transforming.
In the opening for Sailor Stars, Chaos is depicted in a more humanoid form, having pointy ears, long hair, and glowing red eyes. Its entire form is composed of crimson and blackish-blue energy.
Information[]
In the anime, it was sealed away by Sailor Galaxia and eventually managed to corrupt her, but not before she sent her Star Seed, the Light of Hope, out on its own to find "the stars of love and justice".
Eventually, it manages to find Sailor Moon and takes a form that resembles her. This form is Chibi Chibi. At the end, when Princess Serenity manages to free Galaxia on her own and expel Chaos from the body of the powerful Soldier, she explains to Galaxia that no one should try to fight Chaos alone, but that it should forever be held partially in the hearts of all people where it can not overwhelm.
Chaos is an interesting villain that breaks the barriers and precedents set by all previous Sailor Moon enemies. It is a force of evil in and of itself that manages to corrupt a host who wishes to banish it from existence. Unlike enemies from previous seasons; who all had vendettas, plans, reasons, and/or a more complicated method to their evil; Chaos wasn't willing anything to happen. It was a dormant force of evil that inspired evil in the body and mind of the Golden Senshi who tried to destroy it, while it is a thing that can not be erased from the world as long as humans exist. Interestingly enough, Chaos Galaxia was gathering starseeds, essentially eliminating all human life, in order to control the universe.

