Onquanii was a Garan trader who traveled in a Garan merchant vessel and dealt in salvage. He encountered the crew of the USS Voyager while they were taken hostage by a Series 5 long-range tactical armor unit.
Neelix was able to locate Onquanii and Voyager made contact with him through voice communication only. After Neelix outlined the situation, Onquanii agreed to come aboard.
He had a friendly demeanor in Voyager's engineering to assess the situation, and was more than willing to help. Using a hand-held device, he scanned the room to ensure that the bomb was unable to listen in on the conversation. Tuvok assured him that the Starfleet officer had taken precautions, but Onquanni replied that he would be more confident in Tuvok's security measures if the crew wasn't already taken hostage.
Showing great knowledge about the bomb's origins and technology, Onquanii offered to disable the bomb's detonator with his unique transporter system, but asked for the weapon itself as payment, so that he could sell off the salvaged parts. He was particularly interested in the energy matrix, which he said could "power a fleet of starships", and was worth "a thousand dilithium crystals".
Captain Kathryn Janeway refused to hand over the weapon with the energy matrix, concerned with what Onquanii would do with the bomb. Her first officer, Chakotay, commented that Onquanii was quite insistent on obtaining the entire weapon for someone who was only interested in salvage. Onquanii transported off Voyager through his own ship's systems, and immediately attacked, taking out the Federation starship's shields and weapons in order to transport the bomb to his ship. However, the bomb sent a feedback signal through the transporter beam and destroyed the attacking vessel, with all hands presumed lost. (VOY: "Warhead")