Originally a benevolent artificial being named Chaos Header created to bring justice to the universe, having emerged in the nearest galaxy to the Milky Way, the Andromeda Galaxy. Exactly who created her is unknown, yet the being carried immense power and desired to follow her directive to the letter. However, due to this obsession with bringing about justice, Chaos Header believed that violence was the only way to achieve peace and began to force a new order on the universe with an iron fist, corrupting herself into Chaos Darkness. Long before User (Cosmos) set foot on Earth, Chaos Header rampaged on an unnamed planet Cosmos was protecting. She changed the planet's ecosystem and turned it into a wasteland. User, who felt guilty for his perceived failure, vowed to never let another planet fall into Chaos Header's grasp.

Chaos Header first appeared as chaos organisms over a city. Her appearance awed the citizens. Soon, many monsters would become victims of the Chaos Header's virus, such as Golmede, Jelga, Parastan, Eligal, Neldorand, Taildas, Delgoran, Mazalgas and Dolba. Surprisingly, Chaos Header also knew User's identity as Ultraman Cosmos' host.

With knowledge of User as Cosmos' host, Chaos Header traced them all the way to Treasure Base and a semi-possession attempt during Cosmos' transformation resulted with the birth of Chaos Ultrawoman, which is basically Ultraman Cosmos but as a woman.

Ultraman Cosmos pov