Harmonia is the goddess of harmony and the daughter of Aphrodite and Ares. Zeus gave Harmonia to Cadmus after he founded Thebes. The wedding was attended by mortals and gods and goddesses. Harmonia was presented an important necklace made by Hephaestus. Unfortunately the necklace carried a curse said to be vegeance by Hephaetus against her parents. She bore to Cadmus fine children, Autonoe, Ino, Semele, Agave, and Polydorus. Most of the children brought significant trouble to Harmonia. Cadmus left Thebes and took up the cause of another peoples, the Encheleans. These they led against the Illyrians. After ruling Illyria both Cadmus and Harmonia were turned into dragons and they were transported to Elysium.
Next is a discussion of some difficulties with this simple story. The source of the name may be siginificant and meaningful. The name ‘Harmonia’ seems to mean well-joined and is from Indo-European ‘1. ar-, thematic (a)re-, heavy-base arə-, rē-, and i-base (a)rī̆-, rēi-‘, ‘to fit, suit’ and ‘sme, smā̆’, ‘really, truly (emphatic particle)’ and ‘gu̯ē̆nā’, ‘queen, wife, woman’. One can appreciate the connection to love as two lovers well-joined. Hamonia may not be the joining of love and war (Aphrodite and Ares)but rather a play on the various words involved. It may be better to consider Harmonia as the goddess of joining suitable mates than the middle ground that exists between two opposites like love and war. Nemesis is more the goddess of moderation consistent with Greek ideals and is more suitable as a middle ground.
Hesiod, Theogony, line 934 “…Cytherea bore to Ares the shield-piercer.. Harmonia whom high-spirited Cadmus made his wife.” One would expect that Cadmus had done something to deserve a goddess for a wife, especially one so harmonious. Cadmus is credited with bringing the alphabet from Phoenicia. And the alphabet is all about joining letters into harmonious words. Yet there is no mythical reference for this and there is no archeological evidence for the Phoenician alphabet in Greece before the Trojan war. Another possible import from Phoenicia is the cult of Aphrodite, or some aspect of it. Love charms, for example, are related to both the alphabet and to Aphrodite. So Cadmus may have introduced love charms into Greece and had been rewarded with marriage to Harmonia. With this regard the matter of the Minoan culture may be important. When Arthur Evans discovered the Minoan culture he was amazed that such an eloborate culture could be ignored in history. The reason for this is still not known. Evans did propose that the Minoan alphabet was exported to Phoenicia where it may have been modified. The attribution of the creation of the alphabet to Phoenicia may simply be a desire not to recognize the Minoans for whatever reason.Reference on the alphabet
Pindar, Pythian 3,, line 86 “But a secure life was not granted either to Peleus son of Aeacus or to godlike Cadmus; yet they are said to have attained the highest prosperity of all mortal men, since  they heard the Muses of the golden headbands singing on the mountain and in seven-gated Thebes, when Cadmus married ox-eyed Harmonia, and Peleus married the famous daughter of wise Nereus.” How is it that the goddess Harmonia was not able to obtain a secure life for her husband? Pindar goes on to say, “But in time Cadmus’ three daughters, by their bitter suffering, took from him his share of joy;” line 96. But the marriage of Cadmos and Harmonia does have the feeling of the sacred marriage that is used to illustrate the cycles of nature including a beautiful marriage that represents spring and later suffering that represents fall and winter. Perhaps this is a variation on that story.
Then there is the matter of the family of Harmonia. Harmonia is a deity because her parents, Ares and Aphrodite are both deities. The Harmonia became the wife of Cadmus, a mortal. In other cases the child of a mortal and a deity is a hero or heroine such as, Achilles, the son of Peleus and Thetis, Helen, the daughter of Leda, and Zeus, Aeneas, the son of Aphrodite and Anchises, Heracles is the etc. The children of Harmonia are Autonoe, Ino, Semele, Agave, and Polydorus. None of these children are heroes or heroines. Instead they are implicated in a number of tragedies. Worse yet one of her children, Semele, became the mother of a god, Dionysus. So Harmonia has a family that is difficult to undertand in terms of what we have come to expect of families.
There is this from Pausanius, Description of Greece 9.12.3: “The Thebans assert that on the part of their citadel, where to-day stands their market-place, was in ancient times the house of Cadmus. They point out the ruins of the bridal-chamber of Harmonia, and of one which they say was Semele’s into the latter they allow no man to step even now. Those Greeks who allow that the Muses sang at the wedding of Harmonia, can point to the spot in the market-place where it is said that the goddesses sang.”
Images of Harmonia
The Necklace of Harmonia
Homer, Odyssey 11.326: “And Maera and Clymene I saw, and hateful Eriphyle, who took precious gold as the price of the life of her own lord.”
Pausanias, Description of Greece “In Cyprus is a city Amathus, in which is an old sanctuary of Adonis and Aphrodite. Here they say is dedicated a necklace given originally to Harmonia, but called the necklace of Eriphyle, because it was the bribe she took to betray her husband. It was dedicated at Delphi by the sons of Phegeus （how they got it I have already related in my history of Arcadia）,1 but it was carried off by the tyrants of Phocis.”
Pausanias, Description of Greece 8.24.10: “Callirhoe conceived a passion for the necklace of Eriphyle, and for this reason sent Alcmaeon against his will to Phegia. Temenus and Axion, the sons of Phegeus, murdered him by treachery. The sons of Phegeus are said to have dedicated the necklace to the god in Delphi,”