Therefore, its known narrative elements are not a part of the Doctor Who universe as we, on this Wiki, choose to define it. It may have been the basis for a similar story in another medium, however — and that story may indeed be valid.
The Children of Shreeva was an unproduced audio story by Andy Russell.
Following the airing of The Paradise of Death and The Ghosts of N-Space, Russell wanted to give the Sixth Doctor a 40-episode radio series and wrote The Children of Shreeva. The script went through a number of changes over the years and was submitted to Big Finish Productions as a Bernice Summerfield story on 15 April 1999 following the rejection of Asylum.
Gary Russell rejected the story and remarked some years later that he could not remember anything about it, which was likely why he rejected it. Andy Russell submitted a reworked version of The Children of Sheeva, again as a Doctor Who story, on 1 August 2003. (REF: Bernice Summerfield: The Inside Story)