Viorsa's species was a Delta Quadrant race who operated the Kohl settlement. In 2353, the settlement was almost destroyed by a solar flare, forcing five of them entered hibernation using an interactive simulation to keep their minds active.
Unfortunately the simulation tapped into their subconscious minds and created an entity from their fear, known as "the Clown." The Clown tortured them for 19 years before being discovered and destroyed by the crew of the USS Voyager. Sadly only two members had survived. (VOY: "The Thaw")