|This article is about a/an kaijin in Kamen Rider Black.|
This monster appeared in the form of a samurai that came out of the portal caused by a time-traveling device. After a brief fight with it in its samurai form, Kohtaro transformed into Kamen Rider Black. Cobra Mutant escaped into the timestream to pursue two samurai. Cobra Mutant caused them to use the machine to alter people and stop time. Kohtaro followed them into the timestream and ended up on the face of a giant clock where a boy named Mamoru was being held. Cobra Mutant attacked Kohtaro who then ended up hanging from the side of the clock. The two samurai arrived and ended up helping Mamoru.
When Cobra Mutant started to attack them, Kohtaro transformed into Kamen Rider Black who kept Cobra Mutant occupied. When the samurai freed Mamoru, Kamen Rider Black used the broken big hand of the clock to chop off Cobra Mutant's tail and stab it.
Once Kamen Rider Black killed Cobra Mutant with the Rider Kick, the device was destroyed and time was set back to the way it was.
It can extend its tail to constrict and can travel through time.