The Nezu are a race that Voyager attempts to aid when several large asteroids threaten their home planet. From all indications they are atleast a space farring race who mine Galacite from the planet and use orbial thethers to lift the ore some 300km into the planets atmosphere for tranfer to cargo ships.
Following an investigation by Voyager, it was discovered that the asteroids were artificial and intended to destroy key Nezu cities. This was a preliminary strike by a race called the Entanian Order, who used the asteroids to destroy most of the population prior to the arrival of their invasion force.
Information on the Entanian ship was found by Doctor Vatm, a Nezu astrophysicist, and allowed Voyager to disable the ship and the remaining asteroids prior to the invasion.