Despoina

In Greek mythology, Despoina () was the daughter of Demeter and Poseidon and sister of Arion. She was the goddess of mysteries of Arcadian cults who was worshipped under the title "Despoina" ("the mistress"), alongside her mother Demeter, one of the central figures of the Eleusinian Mysteries. Her real name could not be revealed to anyone except those initiated to her mysteries. Writing during the second century A.D., Pausanias spoke of Demeter as having two daughters; Kore being born first, before Despoina was born, with Zeus being the father of Kore and Poseidon as the father of Despoina. Pausanias made it clear that Kore is Persephone, although he did not reveal Despoina's proper name.
In the myth, Poseidon saw Demeter and desired her. To avoid him, she took her archaic form of a mare, but he took the form of a stallion and mated with her. From this union Demeter bore a daughter, Despoina, and a fabulous horse, Arion. Due to her anger at this turn of events, Demeter also was given the epithet, "Erinys" ("raging").
Etymology.
The word, "Despoina" ("mistress", ), is derived from "*des-potnia", "lady or mistress of the house", from PIE *"dóm(ha)os", "house(hold)" [*"dem(ha)-", "build"] and *"potniha-", "lady, mistress"; cf. Greek "domos" and "potnia". The masculine form is "Despotes", "master of the house" (); cf. posis. Related attested forms, written in the Linear B syllabary, are the Mycenaean Greek , "po-ti-ni-ja", ("potnia") and perhaps , "po-se-da-o", and , "po-se-da-wo-ne" ("Poseidon"), which were inherited into classical Greece with identical or related meanings. "Demeter" is possibly a related word, interpreted by some, as "mother of the house" (from PIE *"dems-mater").
Cult of Despoina.
The cult of Despoina is very important in the history of ancient Greek religion. The Arcadian cults come from a more primitive religion. Evidently, the religious beliefs of the first Greek-speaking people who entered the region were mixed with the beliefs of the indigenous population. The figure of a goddess of nature, birth, and death was dominant in both Minoan and Mycenean cults during the Bronze Age. Wanax was her male companion ("paredros") in the Mycenean cult, and usually, this title was applied to the god Poseidon as king of the sea. 
In the myth of the isolated land of Arcadia, the river spirit of the underworld appears as a horse (Poseidon Hippios), as was usual in northern European folklore. He mates with the mare, Demeter, and from the union she bears the horse, Arion, and a daughter who originally had the shape of a mare too. It seems that the Greek deities started as powers of nature, and then they were given other attributes. These powers of nature developed into a belief in nymphs and in deities with human forms and the heads or tails of animals. Some of them, such as Pan and the Silenoi, survived into the classical age. The two great Arcadian goddesses, Demeter and Despoina (later Persephone), were closely related to the springs and the animals, and especially, to the goddess Artemis (Potnia Theron: "The mistress of the animals"), who was the first nymph.
On a marble relief at Lycosura is the veil of Despoina, on which human figures are represented with the heads of different animals, obviously, in a ritual dance. Some of them hold flutes. These could be a procession of women with animal masks or of hybrid creatures. Similar processions of daemons or human figures with animal masks appear on Mycenean frescoes and gold rings. Most of the temples were built near springs, and in some of them there is evidence of a fire which always was kept burning. At Lycosura, a fire burned in front of the temple of Pan, the goat god. The megaron of Eleusis is quite similar to the "megaron" of Despoina at Lycosura.
Sanctuary at Lycosura.
Despoina was worshipped in a sanctuary at Lycosura, west of the town of Megalopolis. Although this cult remained regional rather than becoming panhellenic, this is a very important site for the study of ancient mystery religions. Later, Despoina was conflated with Persephone.
She was known by the additional epithet of Despoine among the general population, just as they surnamed Demeter's daughter by Zeus as Kore (the maiden).
Women who worshiped at the site had to adhere to a dress code that prohibited participants from wearing black or purple, possibly because those colours were worn by priestesses.
Origins.
In the mysteries Demeter was a second goddess below her daughter, the unnameable "Despoina". It seems that the myths in Arcadia were connected with the first Greek-speaking people who came from the north during the Bronze Age. The two goddesses had close connections with the rivers and the springs. They were related to Poseidon, the god of the rivers and the springs, and especially to Artemis, who was the first nymph. Her epithet, "the mistress", has its analogue in Mycenean Greek inscriptions found at Pylos in southern Greece and at Knossos in Crete. Later, Despoina was conflated with Kore (Persephone), the goddess of the Eleusinian mysteries, in a life-death-rebirth cycle. Karl Kerenyi asserted that the cult was a continuation of a Minoan goddess, and that her name recalls the Minoan-Mycenaean goddess , "da-pu2-ri-to-jo,po-ti-ni-ja", i.e. the unnamable "Mistress of the Labyrinth" at Knossos.
Epithet.
"Despoina" was an epithet for several goddesses, especially Aphrodite, Persephone, Demeter, and Hecate. Persephone and Demeter are two of the three goddesses of the Eleusinian mysteries. Perhaps they could be the "Two Queens" referred to in various Linear B inscriptions. At Olympia they were called, "Despoinai" ().
The epithet, Despoina, is related to the Mycenean title, "potnia" (po-ti-ni-ja), that usually referred to goddesses. This divine title could be the translation of a similar title of Pre-Greek origin, just as the title "Our lady" in Christianity is translated in several languages. It seems that the original title accompanied the Aegean mother goddess.
Archaeology.
At the time of a visit to the sanctuary at Lycosura by Pausanias in the second century A.D., the sculptures would have been 300 or more years old. In the second century A.D., a statue of the emperor Hadrian was dedicated in the temple. Coins from Megalopolis, from the Severan period in the early third century, appear to depict a statue from the cult group.
There is a small museum at the archaeological site, housing small finds as well as part of the cult group, while the remains of the cult statues of Despoina and Demeter are displayed at the National Archaeological Museum of Athens. The most significant artifact among its collection is the veil of Despoina, displaying a complex decorative program, probably representative of the types of embroidered woven materials created by contemporary artists. Also displayed are the heads of Artemis, Demeter, Anytos, and a Tritoness, from the throne in the sanctuary.