From Imperial Wiki
The Caretaker is a one-episode super-being who transported the USS Voyager from the Alpha Quadrant to the far side of the Delta Quadrant in search of unspecified biological material that he could use to cure his own illness, so he could continue to care for the Ocampa. None of the crewmembers of the Voyager had what he required, and he soon died, leaving his powerful space station unattended; Captain Janeway destroyed it to keep it from falling into the hands of the Kazon.
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At least one other member of his species is known to exist.