A sporocystian race from outside the Milky Way galaxy, a group of Nacene were accidentally responsible for severely damaging the atmosphere of the Ocampa homeworld sometime around 1370. Possessing advanced technologies, the Nacene were distressed to find that they had destroyed all nucleogenic particles within the planet's atmosphere, making the production of rain impossible. This event was known to the Ocampa as the Warming. With the only source of water on the planet being underground, the Nacene constructed a large subterranean city and led the Ocampa under the surface to their new home. In order to provide the Ocampa with the necessary energy, the Nacene constructed a large space station array that emitted radiant energy bursts that were collected by surface conduits and channelled to the Ocampa city. The Ocampa, who never had any direct contact with the Nacene and were unaware that they were responsible for the Warming, referred to the aliens as Caretakers. Although a male and female Nacene were left behind to operate the Array, Suspiria, the female Nacene, eventually tired of her responsibilities and left the array.
When the remaining Nacene was forced to search the galaxy for a lifeform with a compatible biomolecular pattern from which to create another of his species after he realized that he was dying, he eventually abducted USS Voyager and a Maquis vessel from the Badlands. The Caretaker's search ultimately proved futile and he died before finding a compatible lifeform. In order to prevent the powerful technology of the Array from falling into the hands of the Ocampa's enemies, the Kazon sects, Voyager destroyed the Array. Although the Array had contained the necessary technology to return them home, Voyager's crew hoped that they might encounter the other Nacene on their long journey to the Alpha Quadrant.
In 2372 Voyager made brief contact with Suspiria, who had constructed a small array of her own on which 2,000 Ocampa were living on. Suspiria existed as pure sporocystian energy in a subspace layer or domain and only assumed physical form when dealing with the Ocampa, whom she had helped to develop their hidden psycho-kinetic powers. Suspiria had intended to destroy Voyager for killing her mate, but she was stopped by a toxin that had been developed to incapacitate her. This substance was developed after a study of the remains of the male Nacene and was designed to break down a critical enzyme and cause temporary paralysis. After Captain Janeway showed mercy on Suspiria she returned to the subspace rupture from which she had emerged.