The Uxali were a humanoid species native to the Delta Quadrant planet Uxal. Their planet was a peaceful one, on the path to advancement when an Earth probe, Friendship 1 from across the galaxy entered their atmosphere. It told them about the Humans, about how to communicate, and about how to build antimatter and warp technology.
Prior to this incident, the Uxali had no idea that antimatter existed. One of the early experiments with such particles resulted in a massive antimatter explosion, polluting the once M-class atmosphere with poisonous gas and radiation. Many Uxali were killed, and the few that survived were forced to live in underground caverns that partially protected them from the radiation. In 2378, they made face to face contact with humans from the Federation Starship, USS Voyager, who were sent to retrieve the probe. Their leader, Verin tried to get Capt. Janeway to relocate them to a new home in exchange for her captured officers. Janeway tried to cooperate with Verin till he killed Lt. Joe Carey. After the two other hostages were returned, Janeway was convinced by Lt. Tom Paris and Amb. Neelix to help them restore their planet and neutralize the radiation. With assistance from Uxali scientist Otrin, Voyager was able to restore the skies of Uxal and neutralized the radiation. (VOY: "Friendship One")