Just to muddle/clarify stuff (ALL praise be to Chaos!):
The Shadow out of Time is a HPL story about swapping bodies... with aliens!
Calixis is Latin/Greek (sic) for Chalice, a vessel... maybe the whole sector was/is being shaped to be a vessel/conduit in Haarlock's devilry since the family "discovered" it?
Could the Black Sun or the Tyrant Star be the intrusions or breakthroughs of Haarlock's legacy in the prima materia? "Harbingers" of the Hour of Fate?
...Lest I forget