Isitra Colony First was a colony of the Isitri located in their home system on a moon orbiting a large gas giant. The colony was created with the purpose of separating the population from the main group of Isitri so that they could come up with different, and perhaps better, ideas than those of the Isitri located on Isitra Zero.
At some time prior to 2270, Berlis Aknista, a "troublesome mind", was born on Isitra Colony First. Eventually, he was able to take control of everyone on the planet and then everyone on Isitra Zero as well until the crew of the USS Enterprise was able to stop him. (TOS novel: Troublesome Minds)