Pyris VII was the uninhabited seventh planet in the Pyris system. This system was located in the Alpha Quadrant. (Star Trek VI: The Undiscovered Country, production art) Prior to stardate 3018, several mapping expeditions had revealed no indigenous lifeforms on the planet.
In 2267, the ornithoid lifeforms, from outside the Milky Way Galaxy, Sylvia and Korob established an outpost there for the purpose of learning about the worlds of the Federation. Sylvia became infatuated with sensation, and dangerously irrational. To stop her, James T. Kirk destroyed the transmuter used by the aliens. Without its power, the two aliens were not able to survive on the surface of Pyris VII and died. (TOS: "Catspaw")