Rel'nar was a planet where evolution allowed for the rise of a humanoid species that developed into an industrial age level technology.
At some point, their planet was visited by the Invid with the scientist Tokalyan establishing an outpost on this world. He established a Genesis Pit and began conducting experiments in evolution where he produced numerous gigantic monstrous beings from the world's prehistoric past. This was with the intention of gifting the world to the Regess as a new home but should that fail he intended to use it as a base of operations. The activities of the Invid attracted the attention of the Zentraedi who dispatched a scout to visit the planet where the warrior was mortally wounded by one of the monsters but managed to escape.
Returning to the fleet, he gave his report to Breetai before dying who decided to visit the planet himself in order to learn what had killed the warrior. His Battlepod would be shot down by the native Rel'narians. They managed to communicate with the Zentraedi commander who offered his assistance in fighting the terrors that attacked their cities. Whilst he did so, he was knocked unconscious by the Invid who abducted him but he managed to escape from their Hive. Aiding the Rel'nar, he helped in the construction of a hybrid Rel'nar/Zentraedi satellite in order to summon his fleet. The Zentraedi forces were instrumental in the destruction of Tokalyan's Hive leading to his death and freeing the planet from the Invid threat.
After the destruction of the Invid on Rel'nar, Breetai continued with his mission in searching for the lost SDF-1.