PGM VII.756—794, titled only as “Prayer”, is a simple entry in the Greek Magical Papyri that presents only a prayer with no ritual instructions, except for that tried-and-true vagueism “add the usual” at the end.  The surrounding entries in the PGM don’t offer much in the way of clarification, but they tend to be centered on nocturnal works or dream revelation.  This specific entry, however, is an address to Mēnē, the lunar goddess also known as Selēnē, but which is also being used as another name for Hekatē based on the images and depictions given of Mēnē according to her twenty-eight forms, many of which are classically associated with Hekatē in one way or another.  This page presents an implementation of the prayer in a ritual format for a formal supplication to the lunar goddess Mēnē/Selēnē/Hekatē, and can be used for consecrating talismans as well a la the Consecration of the Twelve Faces of Hēlios; although this is titled as a “consecration”, it can be used as a more general purpose ritual for contacting, communing with, and working with the lunar goddess than just a mere consecration of a charm or tool, although it can certainly be used for that.  This ritual and prayer was first discussed in this 2018 post.

The ritual prayer is as follows:

I call upon you who have all forms and many names, double-horned goddess MHNH, whose form no one knows except him who made the entire world, ΙΑΩ, the one who shaped you into the twenty-eight shapes of the world so that they might complete every figure and distribute breath to every animal and plant, that it might flourish, you who grow from obscurity into light and leave light for darkness.

And the first companion of your name is silence,
the second a popping sound,
the third groaning,
the fourth hissing,
the fifth a cry of joy,
the sixth moaning,
the seventh barking,
the eighth bellowing,
the ninth neighing,
the tenth a musical sound,
the eleventh a sounding wind,
the twelfth a wind-creating sound,
the thirteenth a coercive sound,
the fourteenth a coercive emanation from perfection.

Ox, vulture, bull, beetle, falcon, crab, dog,
wolf, serpent, horse, she-goat, asp, ibex, he-goat,
baboon, cat, lion, leopard, fieldmouse, deer, multiform,
virgin, torch, lightning, garland, a herald’s wand, child, key.

I have said your signs and symbols of your name so that you might hear me, because I pray to you, mistress of the whole world!
Hear me, the stable one, the mighty one,
ΑΦΕΙΒΟΗΩ ΜΙΝΤΗΡ ΟΧΑΩ ΠΙΖΕΦΥΔΩΡ ΧΑΝΘΑΡ ΧΑΔΗΡΟΖΟ ΜΟΧΘΙΟΝ ΕΟΤΝΕΥ
ΦΗΡΖΟΝ ΑΙΝΔΗΣ ΛΑΧΑΒΟΩ ΠΙΤΤΩ ΡΙΦΘΑΜΕΡ ΖΜΟΜΟΧΩΛΕΙΕ ΤΙΗΔΡΑΝΤΕΙΑ ΟΙΣΟΖΟXΑΒΗΔΩΦΡΑ

The two barbarous words in the first paragraph transliterate as MĒNĒ and IAŌ, respectively, and the final block of barbarous words are transcribed into Roman script as below:

APHEIBOĒŌ MINTĒR OKHAŌ PIZEPHYDŌR KHANTHAR KHADĒROZO MOKHTHION EOTNEU
PHĒRZON AINDĒS LAKHABOŌ PITTŌ RIPHTHAMER ZMOMOKHŌLEIE TIĒDRANTEIA OISOZOKHABĒDŌPHRA

On the last day of the lunar month, the classical Henē kai Nea, also known as the Dark Moon, Deipnon of Hekatē, or otherwise the evening leading up to or of the conjunction of the Sun and Moon, prepare an altar oriented towards the North (if in the northern hemisphere, or South if in the southern hemisphere), dressed in fine white, black, or silver cloth with three white candles arranged in a triangle pointing in the direction of the orientation of the altar.  Prepare a plate of food and libations for offering.  Anytime after the twilight of sunset has given away to full darkness and before the twilight of sunrise begins, most preferably at solar midnight, approach the altar and light incense appropriate for the Moon (jasmine, sandalwood, bay laurel, myrrh, camphor, and the like), setting the incense and plate inside the triangle formed by the candles.  Recite the prayer as given above, making the appropriate sounds either audibly (when physically possible to do so) or spiritually and mentally (when not physically possible).  As the 28 forms of Mēnē are being listed, visualize each one taking its place clockwise (if in the northern hemisphere, counterclockwise if in the southern hemisphere) around the triangle of candles, starting at the direction of orientation.  After the recitation of the final string of barbarous words of power, formally present your offerings to her, and issue your charge or make your request of Mēnē, then recite the barbarous words of power once more.  Conclude your ritual with thanks, then leave the candles to burn out on their own.  Dispose of the offerings at a three-way crossroads just after sunset, once the Sun has set but while the Moon is still just barely visible.

Two variants immediately arise based on the above:

1. Alternatively, instead of using an altar, arrange three candles in a wide area on the ground in a circle pointing in the direction of orientation, large enough to stand or walk around within as a circle.  This might be preferred for a more direct encounter with the lunar goddess as a sort of conjuration or incubation of her presence.
2. Another alternative is to perform the ritual at the Full Moon instead of the Dark Moon, using a downwards pointing triangle instead.  This ritual would best be performed outdoors directly facing the Full Moon when the Moon is at its highest point in the sky.  This variant would be preceded and concluded by the additional barbarous words of power from PGM VII.317—318 (see this page on the Charms of the Moon and of Arktos):
   

   ΑΧΘΙΩΦΙΦ ΕΡΕΣΧΙΓΑΛ ΝΕΒΟΥΤΟΣΟΥΑΛΗΘ ΣΑΘΩΘ ΣΑΒΑΩΘ ΣΑΒΡΩΘ

   AKHTHIŌPHIPH ERESKHIGAL NEBŪTOSŪALĒTH SATHŌTH SABAŌTH SABRŌTH

   In this variant, it would be preferred to have the candles put on the ground, and the offering made directly on the ground or into a shallow pit dug into the earth, and left there after the ritual.

A more involved variant involves performing the ritual across the twenty-eight days of a lunar month.  Note that there are fourteen “signs”, the sound-based “companions of your name”, while there are twenty-eight “symbols”, images or representations of the goddess.  By doubling the signs and putting the second set in reverse order to match the relative fullness of the Moon (cf. “you who grow from obscurity into light and leave light for darkness”), each sign can be associated with two symbols:

In this variant of the ritual, the ritual would begin on the Noumēnia, the day of the New Moon (not the Dark Moon), sometime after the Sun and Moon have set and when the twilight of the evening has given away to full darkness.  The ritual area would be prepared as above with three candles (preferably using four sets of three seven-day candles, one set for each week), and the same charge would be given night after night, completing with the final set of barbarous words of power.  However, the central part of the prayer (listing the signs and symbols) would grow, listing one sign and one symbol for each night that passes.  Thus, the first three nights would have the following prayers used correspondingly:

1. The first companion of your name is silence!  O ox!
2. The first companion of your name is silence, the second a popping sound!  O ox, o vulture!
3. The first companion of your name is silence, the second a popping sound, the third groaning!  O ox, o bull, o beetle!
4. …

This would then culminate on the final night, the day roughly of the Dark Moon, by listing all the twenty-eight signs, each sign twice in the proper order according to the proper table, as well as all twenty-eight symbols of the goddess.

A synodic lunar month, from a particular phase to the return to that phase, e.g. New Moon to New Moon, is roughly 29.5 days, and is most common among many Western cultures of reckoning a lunar month.  However, a lunar month of 28 days is closer to a sidereal month, common in Middle East and Asian cultures, which is the length of time the Moon takes to return to its relative position among the background stars, e.g. from the first degree of Aries back to the first degree of Aries.  The shorter period is due to the motion of both the Moon and the Earth around the Sun, as opposed to just the Moon around the Earth.  For this reason, although 28 may be used to approximate either the synodic or sidereal month, one may choose a particular sign or conjunction of the Moon with a star or slow-moving planet at the New Moon to begin the ritual to focus the powers of that sign, star, or planet into the ritual as well as Mēnē’s own lunar forces.