In the frieze of the Great Altar of Pergamon (Berlin), the goddess who fights at Helios' back is conjectured to be Theia
|Parents||Gaia and Uranus|
|Siblings||Hyperion, Themis, Mnemosyne, Rhea, Cronus, Oceanus, Tethys, Iapetus, Krios, Phoebe and Coeus|
|Children||Helios, Eos and Selene|
In Greek mythology, Theia "goddess" or "divine" (sometimes written Thea or Thia), also called Euryphaessa "wide-shining," was a Titan. The name Theia alone means simply, "goddess"; Theia Euryphaessa (Θεία Εὐρυφάεσσα) brings overtones of extent (εὐρύς, eurys, "wide", root: εὐρυ-/εὐρε-) and brightness (φάος, phaos, "light", root: φαεσ-).
Earlier myths 
The Twelve Titans:
Hesiod's Theogony gives her an equally primal origin, a daughter of Gaia (Earth) and Uranus (Sky). Robert Graves also relates that later Theia is referred to as the cow-eyed Euryphaessa who gave birth to Helios in myths dating to Classical Antiquity.
Later myths 
Once paired in later myths with her Titan brother Hyperion as her husband, "mild-eyed Euryphaessa, the far-shining one" of the Homeric Hymn to Helios, was said to be the mother of Helios (the Sun), Selene (the Moon), and Eos (the Dawn).
Mother of the Sun, Theia of many names, for your sake men honor gold as more powerful than anything else; and through the value you bestow on them, o queen, ships contending on the sea and yoked teams of horses in swift-whirling contests become marvels.
She seems here a goddess of glittering in particular and of glory in general, but Pindar's allusion to her as "Theia of many names" is telling, since it suggests assimilation, referring not only to similar mother-of-the-sun goddesses such as Phoebe and Leto, but perhaps also to more universalizing mother-figures such as Rhea and Cybele.
Theia in the sciences 
Theia's mythological role as the mother of the Moon goddess Selene is alluded to in the application of the name to a hypothetical planet which, according to the giant impact hypothesis, collided with the Earth, resulting in the Moon's creation.
Theia's alternate name Euryphaessa has been adopted for a species of Australian leafhoppers Dayus euryphaessa (Kirkaldy, 1907).
See also 
- M.M. Honan, Guide to the Pergamon Museum, Berlin 1904, etc.
- Hesiod, Theogony, 132.
- Graves, Robert, The Greek Myths, 42.a
- Hesoid, Theogony 371; of "cow-eyed, Karl Kerenyi observes that "these names recall such names as Europa and Pasiphae, or Pasiphaessa—names of moon-goddesses who were associated with bulls. In the mother of Helios we can recognize the moon-goddess, just as in his father Hyperion we can recognise the sun-god himself" (Kerenyi, The Gods of the Greeks, 1951, p. 192).
- Smith, William; Dictionary of Greek and Roman Biography and Mythology, London (1873). "Theia"