The pilot of a run-down vessel obsessed with destroying a "beast" in space that devours ships. On Stardate 52542 (2375), Qatai attempted to warn away the U.S.S. Voyager as it was being lured toward the bioplasmic organism, but to no avail as the space-faring creature had convinced the crew, through neurogenic telepathy, that they were entering a wormhole leading to the Alpha Quadrant.
Qatai had been hunting the 200,000-year-old organism for nearly 40 years, and had grown nearly impervious to its telepathic manipulations, but had continually failed to outsmart it. Fortunately, Voyager's holographic Doctor and crewmembers Seven of Nine and the young Naomi Wildman were largely immune to the creature's tricks, and by working in concert with Qatai and his ship, they were able to make Voyager less "tasty" to the organism and caused the ship to be expelled from its digestive system.
Voyager deployed beacons to warn other vessels about the bioplasmic creature before resuming course for home, and Qatai was to retreat to make repairs to his vessel. However, it wasn't long before he resumed his quest — the Doctor, in fact, likened to Qatai to Captain Ahab of the 19th-century novel "Moby Dick." Qatai's ultimate fate is unknown.