[A thing that comes to mind regarding psychedelics in Europe and Christianity generally, is the lack of mention. On the other hand, the Greeks may have been using psychedelics for spiritual purposes in groups settings in the pre-Christian Eleusinian Mysteries.The Eleusinian Mysteries of Greece ran for 2,000 years before they were terminated by the pro-Christian Roman emperor Theodosius 1 in 392 AD. The 2,000 year run is mentioned to suggest they held some continuing value to people. A lot of attention is focused on the secret rites and the use of a drink called kykeon. It’s suggested that the rites lasted 2,000 years because people really did have an experience of the gods, and reason why is because the drink kykeon was laced with entheogens. It’s just speculation. The secrets of the Eleusinian Mysteries may have died with the last of them.]From Wikipedia on the Eleusinian Mysteries:
“The rites, ceremonies, and beliefs were kept secret and consistently preserved from antiquity. The initiated believed that they would have a reward in the afterlife. There are many paintings and pieces of pottery that depict various aspects of the Mysteries. Since the Mysteries involved visions and conjuring of an afterlife, some scholars believe that the power and longevity of the Eleusinian Mysteries came from psychedelic drugs.”
Pasted from <https://en.wikipedia.org/wiki/Eleusinian_Mysteries> Entheogenic theories:
“Numerous scholars have proposed that the power of the Eleusinian Mysteries came from the kykeon’s functioning as a psychedelic agent. Use of potions or philtres for magical or religious purposes was relatively common in Greece and the ancient world. The initiates, sensitized by their fast and prepared by preceding ceremonies (see set and setting), may have been propelled by the effects of a powerful psychoactive potion into revelatory mind states with profound spiritual and intellectual ramifications. In opposition to this idea, other pointedly skeptical scholars note the lack of any solid evidence and stress the collective rather than individual character of initiation into the Mysteries. Indirect evidence in support of the entheogenic theory is that in 415 BC Athenian aristocrat Alcibiades was condemned partly because he took part in an “Eleusinian mystery” in a private house.Many psychoactive agents have been proposed as the significant element of kykeon, though without consensus or conclusive evidence. These include the ergot, a fungal parasite of the barley or rye grain, which contains the alkaloids lysergic acid amide (LSA), a precursor to LSD, and ergonovine. However, modern attempts to prepare a kykeon using ergot-parasitized barley have yielded inconclusive results, though Alexander Shulgin and Ann Shulgin describe both ergonovine and LSA to be known to produce LSD-like effects.Psychoactive mushrooms are another candidate. Terence McKenna speculated that the mysteries were focused around a variety of Psilocybe. Other entheogenic fungi, such as Amanita muscaria, have also been suggested. A recent hypothesis suggests that the ancient Egyptians cultivated Psilocybe cubensis on barley and associated it with the deity Osiris.Another candidate for the psychoactive drug is an opioid derived from the poppy. The cult of the goddess Demeter may have brought the poppy from Crete to Eleusis; it is certain that opium was produced in Crete.Another theory is that the psychoactive agent in kykeon is DMT, which occurs in many wild plants of the Mediterranean, including Phalaris and/or Acacia. To be active orally it must be combined with a monoamine oxidase inhibitor such as Syrian Rue (Peganum harmala), which grows throughout the Mediterranean.”Pasted from <https://en.wikipedia.org/wiki/Eleusinian_Mysteries>