Prax was an officer in the Devore Imperium who assisted Kashyk in hunting down telepaths in 2375. He was bigoted towards all telepaths, and took part in several inspections of USS Voyager to see if it was transporting telepaths.
Prax declined to join Kashyk in sampling Voyager's musical and culinary offerings, as, according to Kashyk, he was "a man of few pleasures."
During the Imperium's third inspection of Voyager, Prax personally oversaw reviews of key areas of the ship. In Engineering, he noted power was running through the transporter system. Told by B'Elanna Torres that it was "routine diagnostic" due to "trouble with our imaging scanners," Prax replied, "The problem is in the primary energizing coils. Focus your efforts there." Later, in the cargo bay, Prax noted that "contaminated antimatter" could interfere with his readings and queried Seven of Nine about whether her Borg bionetic implant gave her telepathic abilities.
When Kashyk defected to Voyager as part of a ruse to locate the telepaths hiding aboard the ship, Prax assumed command of the Devore ship. After revealing his deception during a fourth inspection, Kashyk sent Prax to the cargo bay to rematerialize the telepaths. However, with Voyager having anticipated Kashyk's betrayal, Prax found only containers of vegetables suspended in the transporter as the Brenari refugees escaped via the intermittent cyclical vortex.
Shortly thereafter on the bridge, Prax said he would order the ship's crew removed and delivered to a detention center and Voyager impounded, following procedure described in "Imperative 12, codicil 6." Kashyk overrode him, stating that neither of them would benefit from having the failure on their record. He ordered Prax to make it clear to his teams that "this incident never occurred." (VOY: "Counterpoint")