Thank you for the information. I knew about the Necromanteion in Ephyra (Nekromandio Efiras) from previous research.

The cave that was mentioned earlier may have also been The Great Antrum at Baiae in Italia. Or perhaps the Cave at Atthis.

I've also found remote references to the Universal Eclectic Sect which is supposedly a brotherhood of priests of Hades. Every other reference to this sect seems to lead to the Wiccan cult of a similar name --but I don't think they are the same.

Many authors seem to believe that Hades was worshipped later during the Hellenic period, but only due to his relationship with Persephone.