This rite is simple, powerful and ancient. The deipnon (“dinner” – plural deipna) is an offering left at a crossroads on the dark moon (the last day of the lunar month, by ancient Greek reckoning) for Hekate and the spirits of the dead in Her company. Common foods include cake or bread, garlic, fish, eggs and cheese. Conventional wisdom is that one should leave these offerings and then walk away without looking behind them. The whole offering is left for Hekate; the meal is not shared as in most Greek sacrifices.
For years in the modern Hellenic polytheist communities, a misconception has been floating around about the idea of the deipnon having been a roundabout way to feed the poor. This has become so prevalent that many people are now donating to homeless shelters and food banks in lieu of making proper deipna, and that’s something I’d like to see changed. There is only a single passage responsible for this issue, and it comes from a comic play (that should tell you something) by Aristophanes called Plutus. His character says:
“Why you may ask this of Hecate, whether to be rich or hungry be better. For she herself says that those who have and to spare, set out for her a supper once a month, while the poor people plunder it before ’tis well set down: but go hang thyself, and mutter not another syllable; for thou shalt not persuade me, even though thou dost persuade me.”
If you understand the context of this conversation, you will see that Aristophanes is not referencing an acceptable religious practice of helping the unfortunate, but rather mocking the fact that the hungry poor are so desperate that they will even steal food from an ominous goddess like Hekate. (I’ll note that even in more traditional sacrifices where the resulting meal is “shared” between gods and worshippers, there are still parts that are expressly reserved for the gods alone – one would never set those out for Them and then eat the same items without fear of serious consequences.)
While I wouldn’t want to discourage acts of charity in the gods’ names, in this case I feel it is potentially problematic – in that if you offer food on Hekate’s night, in Her name, but someone else receives and consumes that food, they are unknowingly partaking of an offering that should have rightfully been exclusively reserved for the goddess, and may suffer ill-effects from such. Gifts to the homeless would more appropriately be offered in the name of Hermes, or perhaps Zeus Xenios – but even if in the name of Hekate, they should not be considered the deipnon as such. They certainly shouldn’t be made without a corresponding proper food offering to Hekate directly, for Her consumption alone, at a crossroads (or other liminal place, if necessary, but not at one’s shrine indoors).
Since I’m discussing this, I’ll also mention that there were a couple of other elements to the rites for Hekate at the dark moon that aren’t practiced much anymore to my knowledge (though I do them, personally):
Oxuthumia are household purifications in Hekate’s name – the house is swept and smoked, and pollutions are carried away in a potsherd to the crossroads, thrown away there without looking back. Katharmata are portions of household sacrifices not used (such as waste water and blood), and katharsia are the remains of sacrifices (bones, etc.) – both of these, along with the clay censer used in fumigating the house, were also deposited at the crossroads.
I incorporate these practices by (a) doing a large monthly house cleaning prior to the deipnon, and (b) collecting old offering materials, ashes, and other appropriate items and depositing them where I leave the deipnon.
I also light beeswax candles and incense there, and recite the Orphic Hymn to Hekate in ancient Greek. I then usually pray to Her to also take with Her whatever non-material pollutions I need to be rid of that month. None of these things are attested to in ancient sources, but neither do they seem to conflict with the spirit of the rite.
A good, thorough overview of the deipna and related practices is the essay “Hekate’s Suppers” by K. F. Smith, which can be found in The Goddess Hekate edited by Stephen Ronan, and I believe also in Encyclopedia of Religion and Ethics.
ETA: For those who might want to use it, here is the Orphic Hymn to Hekate, in ancient Greek and then English (Athanassakis translation, which is the best and most accurate, in my opinion):
Lovely Hekate of the roads and crossroads I invoke;
In heaven, on earth, and in the sea, saffron-cloaked,
Tomb spirit, reveling in the souls of the dead,
Daughter of Perses, haunting deserted places, delighting in deer,
Nocturnal, dog-loving, monstrous queen,
Devouring wild beasts, ungirt, of repelling countenance.
You, herder of bulls, queen and mistress of the whole world,
Leader, nymph, mountain-roaming nurturer of youth, maiden,
I beseech you to come to these holy rites,
Ever with joyous heart and ever favoring the oxherd.
