The Gallae(1) were transgendered priestesses of the Cult of Great Mother. Much of what we know about them, and the cult itself, has been pieced together from fragments of contemporary accounts. The cult was a mystery religion, which meant that it's inner secrets and practices were revealed to initiates only.
In the following I present some details of this, taken a variety of sources.
Cybele originated as an earth goddess worshipped in Asia Minor, primarily at Çatal Hüyük. She was known as Kubaba and was earliest depicted as an earth mother -- in plump and heavy forms. The name may be derivative of the local word for cube and may refer to a black meteorite that was associated with Her.
She was also shown seated on a throne flanked by leopards (see left). This form persisted later as well, though the Romans showed lions instead, and these were thought to represent the Goddess's male sons, consorts or priests. She became primarily associated with the concerns of women, protection against one's enemies, the healing of grave illnesses, guardianship of the dead, a granter of boons and a giver of the gift of prophecy.
The Greeks colonised Asia Minor after the Trojan War and found worship of the Goddess everywhere. She was absorbed into their mythology about the 8th century BCE , though not willingly at first. Various stories tell of how a priest of Cybele appeared in Athens attempting to spread the religion. He was killed by the locals by being thrown into a pit. A plague followed and they received an oracle bidding them to appease the murdered man. This they did by building the Metro on (temple of the Mother), which also served as a repository of laws.
Cybele became associated with Rhea and Demeter and was later identified with the former. Rhea was mother of Zeus and others and thus Cybele became known as "Mother of the Gods". She was also considered to rule over Mt Ida, near Troy. This later became important as we she see. Main centres of worship were Pessinus and Pergamum.
A main symbol of the Goddess was a black meteorite that resided either at Pessinus, Pergamum, or Mt. Ida. There seems little mention of a Gallae at this time, though some mention of Corybantes and Metragytes, who were begging priests.
About 213 BCE the Romans were fighting a war with Carthage. It was not going well and panic and uncertainty was the rule. Many superstitious ideas and practices were about that were not Roman in origin. This alarmed the Senate, and to reinstate order, they issued a decree that all books of prayers, prophecies and manuals for the sacrificial cult to be delivered to the city praetor. Nor was anyone to sacrifice in public or in a sacred place according to a new or foreign rite.
Now some of the families in Rome were descended from Trojan emigrants, and prided themselves in their supposed Trojan origin. Rome was considered to be a "New Troy" by many, and thought that its fate might be dependent upon the Phrygian Goddess(2). The Sibylline books declared that "whenever a foreign enemy has invaded Italy, he can only be driven away and vanquished, if the Mother of Mount Ida is transferred from Pessinus to Rome".
A delegation was sent to Delphi to consult the Oracle and then to Pergamun where the ruling King (then allied with Rome against Philip V of Macedon) gave them the statue and the black meteorite that personified Cybele. This was carried on a ship built of pine trees from Mt Ida, through Tenedos, Lesbos, the Cyclades, Euboea, Cythera, around Sicily and then to Ostia (chief port of Rome).
From Ostia the Goddess was taken by boat up the Tiber to Rome. There is a legend that the boat carrying the holy aerolith became stuck in the mud of the port which had begun to silt up. Then a young matron, whose reputation had been tarnished , removed her girdle and tied it to the boat, freeing it easily. From there Cybele was moved hand to hand by the matrons of Rome, to the Temple of Victoria until a Metro on was built in 191 BCE . The black meteorite was adapted as the head of the cult statue. Cybele, like Artemis of Ephesus, was a "black virgin".
Caesar Augustus later rebuilt this temple after it burnt down, and he acknowledged Cybele as chief divinity of the Roman Empire. Cybele's retinue included many priestesses, including Amazonian, transgendered female priest/esse/s as well as traditional masculine functionaries such as the dendrophori (tree-bearer) and cannophori (reed-bearer), and transgendered males known as the Gallae.
At its peek, the Cult of Cybele was rivalled only by that of Isis, and there were temples in all provinces of the Empire. While Cybele was accepted, attitudes towards the Gallae changed over a period of time. When Cybele first entered Rome, there is no mention of the Gallae -- they were later arrivals. Romans were horrified at the frenzy in which the gallae behaved, and by their self-emasculations.
Initially the Gallae were confined to temple grounds, though later they were allowed to roam city streets with other followers. Some Emporers banned Roman citizens from taking part in the rites. At other times, rich and influential families patronised the temples.
Cybele had a reputation for miracles and retribution. Apart from the re floating of the ship carrying the holy relic (see above), She was also held responsible for good crops and military victories (such as the one over the Carthaginians after She entered Rome. At other times She appeared to uphold her own and her follower's honour.
When the Battakès intended to harangue the crowds in the Forum, he was driven from the Rostra by a tribune Aulus Pompeius who called him a charlatan and the crowd hurled insults at him. The tribune was taken with a burning fever and died three days later, whereupon the Battakès reappeared at the Forum and a repentant populace honoured him with gifts.
On another occasion a lady of noble aspirations entered the Aedes Magna Matris and stole a string of pearls from a statue of Cybele. Several days later she was found strangled to death with them. You didn't muck around with the Magna Mater!
The early Christians were determined to destroy the cult and St Augustine condemns Her as a "demon" and a "monster" and the Gallae were "madmen" and "castrated perverts" (hardly an unbiased opinion). In the 4th century CE Valentinian II officially banned the worship of Cybele, and many of her followers perished at the hands of zealous Christians.
Justinian continued the persecution of the cult and the Gallae. Under his reign, transgendered persons, and those indulging in same sex eroticism had their property confiscated, sacred texts burned, temples raised; they were tortured, forced to commit suicide, or burned alive.
By the start of the 6th century CE, the Cult and the ancient Gallae were extinct. Elements of the cult were transferred into Christianity in a manner similar to that of Isis. There is a much of Cybele and Isis in the Virgin Mary.
(1) Gallae is derivative of Latin for chicken or rooster. Historically the Gallae were referred to as Galloi or Galli (plural), or Gallus (singular). This reflects I think how they were seen by those archivists whose works have survived -- as deviant males. However, this little red hen uses the feminine version of the title, reflecting current use for transgendered males.
(2) The fate of Troy had depended upon the the wooden Palladium, the Statue of Pallas-Athena, which Odysseus had stolen.