The Kromon required a constant supply of water to live. All the Kromon were linked to the consciousness of their royals. If the queen that controlled the Kromon's instincts died, they stopped functioning. (AUDIO: The Creed of the Kromon)
The Kromon could build giant biospheres and possessed advanced machines and gunships. They stole this technology, along with the philosophy of management, from a company that exploited the planet Kromon. (AUDIO: The Creed of the Kromon)
The Kromon originated from the planet Kromon. A fleet of company ships arrived, and this company exploited Kromon for its minerals by tearing down trees, blasting mountains and diverting rivers. They built a new sun, causing the clouds to disperse and the rain to stop. The colonies died in their hundreds, and the Kromon spent a thousand years overcoming the invaders. They found way of overcoming the company, stealing their machines and absorbing their philosophy of management. This philosophy became the Kromon's creed.
The Kromon first appeared in the Eutermes zone when C'rizz was a child after Kromon's water had run dry, doing the same to Eutermes what the company had done to Kromon. They enslaved the Eutermesans, using them as slave labour to work in their habitat domes. Years later, the Eutermesan L'da was declared the queen and made into a Kromon hybrid to breed more Kromon. After C'rizz killed L'da, Charlotte Pollard began undergoing the process of becoming the new queen. The process was reversed after the Eighth Doctor provided Charley some Salander antidote. After Charley's release, the water supply was cut off from all of the Kromon biospheres by the Oroog and Salanders; all of the Kromon royals quickly died, leaving the Kromon directionless and motionless. (AUDIO: The Creed of the Kromon)