Neo Organism

The Neo Organism is a genetically engineered pool of living fluid that serves as It lacks emotions and believes itself to be a god. It first appears as the main antagonist of Kamen Rider ZO and later returns as the true antagonist of Movie War 2010.

Kamen Rider ZO
The Neo Organism was the result of Doctor Mochizuki's attempts to create a "perfect lifeform". Upon its creation, it assumed the appearance of the Mochizuki's son Hiroshi.

Trapped in a pool by Mochizuki and unable to complete its evolution, the Neo Organism created an extension of itself called Doras to seek out Hiroshi and use him to force Mochizuki to complete it. Kamen Rider ZO then attempted to stop Doras's plans. Doras created several Doras Monsters to deal with Kamen Rider ZO while he captured Hiroshi.

ZO rescues the boy buts ends up getting absorbed by Doras. However, Hiroshi's pocket begins playing music, causing ZO to break free from Doras. The Neo Organism was defeated when Mochizuki destroys its life support, while ZO kills Doras with his ZO Kick.

Kamen Rider Decade: All Riders vs. Dai-Shocker
Doras appeared in the movie All Riders vs. Dai-Shocker as a member of the Dai-Shocker. He was part of the army of revived monsters that fought against the gathering of 25 Kamen Riders and was presumably wiped out along with them.

Movie War 2010
A second Neo Organism was created by Super Shocker scientist, Super Doctor Shinigami. It was released by Bee Woman after she was defeated by Electro Magnetic Wave Human Tackle. Upon being release, the Neo Organism absorbs Bee Woman and spawns Doras. Doras then attacks Colonel Zol and goes to fight Kamen Rider Decade. While at first overpowering the Rider, Decade's allies from the Nine Worlds soon arrive and assist Decade by using their Ultimate Forms to destroy Doras.

Neo Organism then takes control of the Super Crisis Fortress, but it gets destroyed by Kamen Rider Double. In response, Neo Organism absorbs the Dummy Dopant and transforms into its final form, Ultimate D. Decade then creates a Ride Card for Kamen Rider Double, turning him into CycloneCyclone and JokerJoker and allowing them to destroy Ultimate D.

OOO, Den-O, All Riders: Let's Go Kamen Riders
After Shocker succeeded in achieving world domination using Shocker Greeed, it assimilated many members from various groups that didn't get the chance to manifest, including Doras. When the Kamen Riders started to reappear and attack Shocker, Doras went to battle ZO.

Kamen Rider x Super Sentai x Super Hero Taisen
Doras was once again revived as part of Dai-Shocker in Super Hero Taisen. He attempted to kill Gokai Blue after he tried to attack Decade, forcing Gokai Blue out of his transformation. He was then killed by Emperor Marvelous before he could finish Joe off.

Heisei Rider x Showa Rider: Kamen Rider Taisen feat. Super Sentai
Doras was resurrected again as part of the Underworld Empire Badan. He was destroyed by Kamen Rider Hibiki.

Trivia

 * The Neo Organism is similar to Cell, as both seek to obtain a perfect form.