Rhizon is the commander of the Cryog invasion force and the primary antagonist of the majority of Godzilla: Rulers of Earth, before he is overtaken by his much more wicked and dangerous superior, Karkaro.
Rhizon resembles the other members of his race, except he possesses an ornate frill that extends from his upper body to behind his head, indicating his higher rank. He also possesses a large scar over his right eye.
Rhizon is a very skilled military commander and master manipulator. He is shown to be incredibly resourceful and intelligent, like how he managed to survive his ship and entire crew being destroyed by Biollante, and took on the disguise of a Devonian refugee in order to orchestrate the destruction of the Devonians by the humans.
Despite his military skill, Rhizon appears to have severe anger management issues. When he is frustrated, he will make rash decisions that often result in crushing failure or the loss of many of his men. Rhizon is a very sadistic and ruthless individual, and is incredibly hostile to his subordinates. He frequently insults and injures them whenever things do not go according to his plan. Rhizon does not seem very concerned for his race's well-being, as he sees the Earth as a prize that he wants to personally conquer, cementing his legacy as a legendary commander. Rhizon sees other species as inferior, and does not hesitate to brutally massacre dozens of humans and Devonians. Rhizon also harbors an obsessive hatred of Godzilla, whom he blames for all of his failures.
Despite Rhizon's threatening and fearsome exterior, he actually greatly fears the Cryogs' emperor, Karkaro. Karkaro proves to be much more despicable and evil than Rhizon, and as punishment for Rhizon's inability to conquer Earth he plans to completely destroy all life on the planet with the Trilopods while Rhizon watches, and then kill him afterwards. This shows that Rhizon may not be entirely evil, or at least not to the extent of Karkaro.
At some time in his past, Rhizon was Karkaro's most trusted general. An unknown incident occurred which apparently ended in Karkaro's death, and Rhizon assumed command of the Cryog forces. Rhizon led his forces to Earth, intending to conquer it and assume all of the glory himself. Rhizon formed a shaky alliance with the Devonians, who were residing in Earth's oceans, and agreed to partition the planet between the two races after humanity was defeated. Rhizon regarded the Devonians as inferior, and intended to eliminate them after they fulfilled their usefulness. After the Devonians' monster Destoroyah failed to kill Godzilla, Rhizon ordered the upgraded Gigan to free a ship from Area 51. After the ship was released and activated, Gigan lead it to Las Vegas. Godzilla arrived and attacked Gigan, along with the human-built robot M.O.G.U.E.R.A.. Gigan subdued Godzilla, and the UFO stole his DNA and transformed into Orga. Orga proved to be unstable, and turned on Gigan. Suddenly, a size-changing robot called Jet Jaguar arrived and made Orga explode, then helped Godzilla double-team Gigan. Rhizon ordered Gigan to retreat and ordered another ship to take away Orga's remains while they regenerated.
Shortly afterward, Rhizon's ship was assaulted by CKR and Jet Jaguar. Though the attackers left before they could kill Rhizon, the ship was badly damaged and Rhizon attempted to get the Devonians to help repair it. To Rhizon's shock, the Devonian king revealed that he intended to betray the Cryog, and unleashed his race's new monster, Biollante, to destroy the Cryog ship. The ship was destroyed and all of its crew was apparently killed, but Rhizon survived and escaped. Rhizon took the form of a Devonian, and approached CKR, offering to help them destroy the Devonians before they attacked the surface. CKR mistakenly trusted Rhizon, and launched a nuclear strike on the Devonians' underwater capital, destroying it. Rhizon then revealed his true form and murdered the CKR scientist that worked with him, and escaped to Russia.
In Russia, Rhizon took the form of an old man and took the name Dyachenko, posing as an industrialist. Planning revenge on Godzilla, over the next few years Rhizon's company produced an army of mass-produced MechaGodzillas and began selling them to world governments, claiming it would be an efficient way to protect their countries from kaiju attacks. When Godzilla showed up in Boston, Rhizon obtained permission from a U.S. Senator to unleash his MechaGodzillas against Godzilla. The city was completely devastated in the battle, but Godzilla destroyed most of the MechaGodzillas. Rhizon unleashed his newest weapon, Mecha-King Ghidorah, and abducted Godzilla, carrying him to his robotics facility in Russia, where more MechaGodzillas were waiting. The mechanical monsters nearly overcame Godzilla, but the monster Anguirus arrived and helped Godzilla destroy the MechaGodzillas. Mecha-King Ghidorah broke free from the Cryogs' control and escaped into outer space. Defeated once again, Rhizon ordered a ship to pick him up and take him back into space, along with the two MechaGodzilla units that had survived.
While waiting just outside of Earth's orbit, Rhizon's ship was attacked by SpaceGodzilla. Rhizon hastily ordered the MechaGodzillas to attack, only for them to be frozen in the vacuum of space, allowing SpaceGodzilla to easily destroy them. Rhizon then deployed Gigan to fight SpaceGodzilla off, but he too was defeated and left adrift in space, while SpaceGodzilla descended to Earth.
Shortly after, Karkaro's ship arrived behind Rhizon's, much to Rhizon's shock. Karkaro forcibly boarded Rhizon's ship and took command of the invasion, vowing to punish Rhizon for betraying him in the past. Karkaro unleashed the Trilopods on Earth, and forced Rhizon to watch as they easily mowed through Earth's kaiju.
- Rhizon shares many similarities with Kuronuma, the sadistic leader of the Black Hole Planet 3 Aliens from Godzilla vs. MechaGodzilla. At one point, he even says the line "MechaGodzillas, beat Godzilla to death," a line spoken almost exactly word for word by Kuronuma.
- Rhizon's name is not revealed until issue #20 of Godzilla: Rulers of Earth. Up until then, he is simply referred to as the "Cryog leader." He also briefly takes the name "Dyachenko" while posing as a Russian businessman.