A race of rather short aliens conquered by the Irkens. They are highly intelligent, and create all sorts of famous super technology, including the Universe's Most Comfortable Couch, the Massive, numorous flight crafts and countless weapons. They design all of the "liquid gear".
Vort is now Irk's top military research prison. All of the Vortians are enslaved.
Little known fact:
Captain Lard Nar of the Resisty
is an escaped Vortian prisoner. Reference- Invader Zim, episode "Backseat Drivers From Beyond The Stars"
Also appears in episode "The Trial", though it was never made.
Invader Zim, after made known for his destructive personality, was sent to Vort before it was enslaved to excell at miliraty research. There he worked with the Vortians on the first designs for the Massive.