An evolved form of Chaos-Header’s physical body, born when it copied not only Ultraman Cosmos’ physical form, but also his fighting abilities and tactics.
This form can release 50 times more Chaos Energy than a single unit of Chaos-Header.

Chaos-Header managed to get hold of Musashi, copy Cosmos’ powers, and materialize them. It began to battle with Cosmos and defeated him with a series of Impeding Wave and Chaos Prominence attacks.
It then returned to light virus form and imprisoned Musashi.
TEAM EYES were eventually able to free him, and they battled again. This time Chaos-Ultraman had Chaos-Neldrant II on its side, but when it was hit with the Eclipse Blade its cells began to panic, and vanished after being hit by a Cosmium Beam.

From that point onward it was thought to be annihilated, but its abilities evolved and it reappeared in the D-9 Area. As Cosmos Eclipse Mode entered the scene, it powered up to become Chaos-Ultraman Calamity.