The Ardanan parasite was a microscopic lifeform created by Ardanan genetic engineering sometime prior to the mid 23rd century. The parasites were designed to enhance artistic abilities by embedding themselves into the brain of a host organism, and extending long tendrils through the brain, making connections between otherwise unrelated sensory and cognitive centers.
The first individual to volunteer to be host to these parasites was Soske Busk, the son of Moran Busk, designer of the Cloud City of Stratos. With his new enhanced mental abilities, Soske Busk was able to make his father's work a reality, creating the city's powerful anti-gravity engines and its art and music based navigational system.
Over time, it was determined that the parasites would be introduced only into Stratos's Sentinels -- individuals responsible for running and maintaining the physical workings of the city. However, following the Great Disruption that ended with the abandonment of Stratos, many of these parasites were killed along with their Sentinel hosts. By the late 24th century, only a few specimens remained, contained in small carns, or bio-magnetic chambers, kept as museum pieces. Most knowledge of the parasites also disappeared, though some information was preserved in old texts.
In 2377, when the USS da Vinci was assigned to prevent the imminent crash of Stratos onto Ardana, Crewman Fabian Stevens inadvertently opened one of these carns, and became infected by the parasite inside. The new neural connections made by the parasite enabled Stevens to intuit the art-based operations of Stratos's controls; howver, because of the differences between Ardanan and Human brain chemistry, the parasite spread to his reticular activating system, affecting his autonomic life functions. The parasite was eventually killed off by putting Stevens into a coma, thus denying the parasite of any stimuli. (CoE eBook: Signs from Heaven)
- These lifeforms are never given a formal name in the story, and are simply called "the parasites" throughout.