Halassi

The Halassi were a species who owned the Halassi Androvar. They resembled humanoids with their heads split in two by a diagonal slash; they could separate the halves at will and hide objects inside. Their internal structure was blue and slimy. While most of them looked like humans with slashes across their face, some were pale white and bald.

History
Their King, Hydroflax once raided their planet in "blood and joy", during which the diamond was driven into his skull by an explosion in the Halassi Vaults, and the Halassi tasked River Song to retrieve it.

After fulfilling her mission, River and the Doctor boarded the Harmony and Redemption cruise liner which, as she was an archaeologist from the future, River knew was about to be destroyed by meteorites. (TV: The Husbands of River Song)