Tzun

The Tzun were a humanoid race native to S'Arl.

Technology
The Tzun were known for their genetic technology. They were capable of creating nanites which could separate the DNA of a living hybrid organism. (PROSE: First Frontier)

The Tzun used the Tzun Stormblades as spaceships. These Stormblades had graviton shielding and terullian hulls. (PROSE: The Dark Path)

History
The Tzun were a spacefaring species by at least 23,000 BCE. Shortly after developing space travel, they fought the Darklings of Yuggoth, which corrupted their DNA. They perfected genetic engineering and began integrating new species into their Confederacy by combining their DNA with theirs.

This resulted in the creation of three sub-species of Tzun. There were the pure Tzun, who were not genetically modified; the small grey S'Raph with big heads and black eyes, which had their visual perception expanded to see into the infrared and ultraviolet; and the Ph'Sor, whose DNA was combined with the natives of the planet they were colonising.

In 1957, the Tzun attempted to invade Earth with the aid of, but were defeated by the Seventh Doctor. (PROSE: First Frontier)

In 1983, a Tzun, nicknamed Tony, was a member of Isaac Summerfield's team. (PROSE: Return of the Living Dad)

In 2172, the Tzun attempted to conquer the Veltrochni. (PROSE: First Frontier) Though the Tzun were successful at the beginning, as the war carried on the Veltrochni packs joined forces and fought back. They drove the Tzun off, destroyed many of their colony planets and effectively collapsed the entire confederacy. The Veltrochni became renowned for their power after this. (PROSE: The Dark Path) After this, the Veltrochni gained the Tzun's advanced weaponry. (PROSE: Mission: Impractical)

At some point before 2371, the Tzun had lost control of the Antares system. (PROSE: Lords of the Storm)

In the 26th century, Hamilton Smith, professor of alien-human interaction and integration, had theories about the Tzun. (PROSE: Dry Pilgrimage)

In 3174, some Tzun were housed inside the Habitat. (PROSE: Burning Heart)

In the 40th century, Green Fingers had worked with Tzun. (PROSE: Placebo Effect)

Circa 2,000,000, Sha'ol the Tzun and Karthakh the Veltrochni were working together. (PROSE: Mission: Impractical)

Other references
The Tzun were mentioned by the First Doctor as an example of hostile aliens, alongside Daleks. (PROSE: Salvation)

Bernice Summerfield could speak ancient Tzun. (PROSE: Sanctuary)

Penelope Gate's time machine had a Tzun battery powering it. (PROSE: The Room With No Doors)

Behind the scenes

 * Creator David A. McIntee invented the Tzun for a 30th Anniversary story he pitched to Virgin Books, in which Susan Foreman would have returned as a villain, trying to give the Tzun time travel. In that pitch, they were insectoid.