Commander Bosaal was the captain of a ship caught in the Void. He was from a Delta Quadrant species that possessed a bilateral ridge running vertically along the front of their heads to their chest. (VOY: "The Void")
However, when he saw Fantome aboard Voyager, he described him as vermin. Members of Fantome's species, who were native to the Void, had infested Bosaal's ship, causing engineering problems. After Voyager beamed Fantome's people off Bosaal's ship, Bosaal became an ally of Captain Janeway's and offered to help their ships escape the Void.
Voyager chief engineer B'Elanna Torres said she needed to build a polaron modulator to generate the energy to escape the Void. Bosaal produced one, but he was soon found to have stolen it from another Void-trapped ship after he killed its crew. In Janeway's belief that using the device would make her and the crew of Voyager accessories to murder, she threw Bosaal and his ill-gotten polaron modulator out of the alliance.