Dremk was a former Malon core laborer aboard a waste export vessel commanded by Fesek. Dremk was believed dead by his crew, having "died" from theta radiation poisoning at some point prior to early 2375. However, he had not died and, in fact, had instead become resistant to theta radiation, where he continued to survive unseen aboard the vessel. He remained undetected due to the irradiation of his body tissues, which allowed him to blend in to the background radiation on the freighter.
Dremk's personality and appearance were drastically altered. Disfigured and mentally unstable, he harbored great anger towards the industry that had caused his predicament. As an act of revenge, Dremk carried out a series of sabotages against his ship. Believing that the ensuing catastrophe caused by its destruction would bring an end to the waste transport industry. Due to his deranged condition, he was unconcerned by the collateral damage his "revenge" would unleash- including the deaths of all but two of the crew, Fesek and Pelk. The latter believed him to be a vihaar, a semi-mythical creature- formed from theta radiation- spoken of in the myths and folklore of the various freighter crews over the years.
Adrift and out of control, the massive vessel threatened to contaminate the entire star system. With the assistance of the crew of the USS Voyager, an attempt was made to neutralize the ship. Neelix, Chakotay and B'Elanna Torres were sent to the freighter along with Fesek and Pelk to regain control. However, Dremk observed their arrival and began stalking them. He succeeded in killing Pelk, and nearly managed to kill the others during their attempt to regain control of the freighter. After attacking Fesek and Neelix, he revealed himself to Torres. Dremk was rendered unconscious by Torres while attempting to complete his plan. He was ultimately killed when the freighter exploded within the corona of an O-type star.
Whether or not Dremk was pretending to be 'the vihaar' is unknown, though the parallels (both literal and allegorical) between the mythical creature and what he had become did not go unnoticed. In particular, by B'Elanna Torres, who advised Fesek to tell his own people "the vihaar is real." (VOY: "Juggernaut")