The rulers had hoped the dissidents, branded "criminals," would be devoured by the vicious beasts in the Onderon wilderness that had migrated over an oxygen bridge from the moon of Dxun. However, the rulers were proven wrong. Over time, the outcasts succeeded in taming the beasts, using them as winged war mounts for their campaigns against the walled city of the Iziz army. They managed to establish themselves as powerful Warlords, with great armies of vicious creatures at their command known as the Drexl. Soon Onderon would experience a permanent war.
The conflict between the corrupt monarchy and the Beast Riders escalated to the point that Queen Amanoa sought aid from the Republic. Jedi Master Arca Jeth's students, Ulic Qel-Droma, Cay Qel-Droma, and Tott Doneeta, were sent to deal with the situation. The Jedi learned that the queen's daughter, Princess Galia, had been kidnapped by the beast riders. Upon finding her, they learned the captivity was a ruse intended to hide Galia's true intentions: escape from the dark side-influenced royalty and marriage to the Beast-Lord, Oron Kira.
Queen Amanoa would not stand for any such marriage and attacked the Jedi with her dark side powers. Simultaneously, the Beast Riders attacked and took Iziz. Amanoa was defeated and Galia married Oron Kira. Their marriage ended the war between the city-dwellers and Beast Riders, finally granting a tenuous peace for Onderon.
The Beast Riders would fight once again—in defense of Onderon—during the Great Sith War against the allied forces of Exar Kun and the Mandalorians. They successfully drove the Mandalorians to Dxun, where Mandalore was killed by native wildlife. The Beast Riders also fought during the Mandalorian Wars, in which Onderon was one the first planets to fall to the Mandalorian warriors.
Many Beast Riders perished in the liberation of Onderon, and most survivors ended up in Iziz seeking employment as mercenaries. Many, however, became mere street thugs and criminals. Some of these included Bakkel and Panar, whom the Jedi Exile encountered while seeking holodiscs for Dhagon Ghent so she could meet with Jedi Master Kavar in the Iziz Royal Palace.
It is unknown which side the Beast Riders took in the Onderon Civil War, but it is assumed they were divided over the issue. Their beasts, on the other hand, aided the General Vaklu's Confederates and Sith allies due the Sith practicing a ritual in Freedon Nadd's tomb to control the beasts. It is believed that they largely sided with the Royalist supporters of Queen Talia.
Following the war, the Beast Riders faded into history, but a number were still present when Leia Organa Solo fled from the reborn Emperor to Onderon