The Naiad is a special breed of Queen created by the Scylla Brood.
Naiadi ususally stay near the central hive to watch over maturing Zerg, but their natural weapons and special abilities make them quite formidable attackers as well. The Naiad's primary function is to manipulate its "offspring"; for instance, they engineered the Zergling morph to the Creepling, a breed that can "merge" with Zerg Creep to act as an effective Hive defense unit.
On the battlefield, however, the Naiad's primary function becomes the manipulation of the enemy. The Naiad possesses two seperate forms it may take on depending on the needs of its Protoss Master, Flyer Form and Crawler Form. While away from its "Mother-Hive", a Naiad tends to take on Flyer Form in order to utilize its assault abilities. One such ability is to be launched from a distance; a tiny, remora-like parasite attaches itself to the target, 'bonding' with it should the target be organic. The parasite allows higher Zerg strains to see whatever the target sees, and cannot normally be removed without killing its host. However, with the use of nano-conveyed anesthetic and attenuated laser technology to surgery, these parasites can be safely removed. A similar organism known as the Broodling may also be spawned in a similar manner, although used as alternative means of spawning.
It takes time for the Naiad to produce these creatures, though the rate of reproduction may be increased through the use of gamete meiosis. In the meantime, the Naiad is able to spray its victims with a thick acidic Web, slowing them down slightly and eating through their armor before dissolving. Most powerful of the Naiad's abilities however, is its ability to produce cleansing anti-toxins. Once released onto an infested structure (usually a Terran Command Center), these anti-toxins quickly remove infesting organisms from the facility, bringing the structure and those inside it out from under the control of the Zerg. A similar ability is utilized in order to take control of enemy Zerg structures.
The Naiad evolves and adapts over the course of time, growing in size as it does so. In it's Crawler Form it maintains base nurturing and defense duties, including laying Swarm Clutch eggs that hatch into specialized Broodlings, or excreting small patches of Creep in order to produce a new Zerg colony. Like many other Zerg ground units, the Naiad can burrow in its Crawler Form. Also, the Naiad can enhance the regeneration speed of "friendly" Zerg structures, and can spawn numerous types of its own "Colony" structures upon the Creep. The Naiad's primary production structure, the Creep Colony, acts as a mobile Creep-producing node, and can mutate into a Shrieker Colony when the need arises. The Shrieker Colony possesses special anatomical sensory organs that can detect cloaked units in a fairly large area around it, and its shrieking can double as both a Zerg alarm sytem and an encouraging battle cry.
The most powerful of the Naiad's spawn structure abilities lies in its power to produce a Nesting Colony. Nesting Colonies perform three vital functions that no colony can survive without: producing the Creep, which all Zerg structures require in order to be built, giving birth to Larvae that can mutate into the various Zerg breeds and digesting Minerals and Vespene gas to change into a nutrient form that Zerg can use to feed their mutations. Unlike the Hatchery, the Nesting Colony requires a small patch of Creep upon which it must be created. Also, the Larvae of the Nesting Colony can only mutate into Drones, Broodlings, and Overlords, making a Zerg colony run by a Hatchery far superior to the small Nesting Colonies of the Naiadi.