Phil Hine posted a link to his account of ritual experimentation he was involved with in the 1990’s. An excerpt reads:
The ancient Greeks created special places – often underground – where visitors could commune with the spirits of the dead. These places were called psychomanteums. The following is a description of the Nyarlathotep Coven’s experiments in recreating a psychomanteum for the purpose of two-way traffic with Lovecraftian liminal spaces and their denizens.
Read the whole magilla:
https://enfolding.org/one-from-the-vaults-the-psychomanteum-working/.
Cthulhu statue by Maria Strutz