Alliance with the Irken EmpireThe Vortian race was originally in alliance with the Irken Empire, and made many powerful weapons for them, such as the MegaDoomer Combat Stealth Mech. They also designed most of the Massive, the flagship of the Irken Empire. However, the Vortians' alliance with the Irken Empire ended on a sour note when Zim created a hideous blob creature on Vort Research Station 9, which devoured Tallest Miyuki, and later Tallest Spork. Because the blob was produced in a Vortian facility, the incidents were blamed on the Vortians.
EnslavementPlanet Vort, homeworld of the Vortians, was conquered by Invader Larb. The Vortians are now forced to create advanced weaponry for the Irken Empire, helping them take over more planets. Vortian Prisoner 777 is one such prisoner, and despite apparent annoyance with Zim's calls for tech support, had no qualms with freely giving away vital information about the makeup of the Massive.
The Resisty is a resistance group formed by a Vortian called Lard Nar against the Irken Empire. Many other Irken-enslaved sentients have joined this group, although Lard Nar is the only Vortian. The Resisty planned to destroy the Massive by shooting at the sidepods, the ship's one weakness, but they fail and vow to come back. The Resisty's ship was destroyed when "Shrinky Self-Destruct" was activated. This caused the ship to shrink to a microscopic size and explode. Apparently, this was one of the last Vortian ships left. This would imply that around Vort's conquering, the rest of their ships were destroyed by the Irkens.