- The Chaos Header is the show's major villain. Their modus operandi involves transforming monsters or cloning them into corrupted version of themselves. This is also a trouble for any docile monsters, as their free will and what's left of their sanity was quickly stripped away and turned into the classical brutish monster that the Ultras usually fight.
- Shown in the right is Renki, a samurai ghost born from a pair of Star-Crossed Lovers. His revival into the present day is a huge walking nightmare fuel; his face is constantly angry with shining red eyes and his mask even brings in mind to Kuchisake-onna, a popular onryo in Japan. The giant is constantly spouting "Why did you disturb us?" in a slightly chilling and disturbing manner.
Nightmare Fuel / Ultraman Cosmos