Nixtus III was the home for both the Zanthians and the Jangrofens. The Twelfth Doctor considered it to be “one of the most enlightened civilisations in the galaxy”.
While searching for the siblings of the Hazandra, the Twelfth Doctor, Grant, Lucy and Jennifer went to the planet. (Ghost Stories)
The two main life forms of the planet, the Zanthians and the Jangrofens, evolved side by side over millions of years, stemming from the same ancestor race. Many wars broke out between the two races, until a treaty was signed to allow a symbiotic relationship between the two sides. For thousands of years, the two races lived as one, until it was discovered that the bonding between them corrupted the Jangrofen DNA, slowly causing their extinction. It was at this moment that Harmony Shoal offered to replace the void left by the Jangrofens, offering another symbiotic relationship, and the proposal was accepted by the Zanthians. With the help of the Alcyone, Harmony Shoal shut down the decentralised nervous system of the Zanthians to successfully overpower and replace them. The Twelfth Doctor and Grant, with the help of Lucy, Jennifer and Nemika, retrieved the gemstone and convinced the Zanthians to rebel against Harmony Shoal, saying that they could live without searching for another species to bond with and without burying themselves. (Ghost Stories)