Mixtus II was the inhabited second planet in its system.
In 2380, the orbit of Mixtus III's fifth moon began to decay, threatening to impact the surface and cause catastrophic damage. The planet's inhabitants requested assistance from the United Federation of Planets, who dispatched the USS Vancouver and USS Cerritos to carry out a controlled demolition of the unstable moon.
Despite the danger the moon posed to Mixtus III, a wealthy representative from Mixtus II insisted that the moon should not be destroyed because it blocked pollution from Mixtus III that would otherwise land on his planet. This delayed the demolition until Captain Carol Freeman of the Cerritos discovered that Mixtus II was only inhabited by the representative and his wife. Freeman immediately ordered the moon to be imploded, which, despite the representative's protest, was carried out without incident. (LD: "Cupid's Errant Arrow")
This planet was not fully seen, appearing only as a simplified graphic on a viewer.