Oshtur is an Elder Goddess, born from the Demiurge and sister to Gaea, Set and Chthon. Before the degeneration of most of the Elder Gods into demons, she left Earth, took to the stars and became the Goddess of the Skies.
One day, Oshtur was watching children play and she saw a blind child. Despite his disability, the child enjoyed life and managed to smile. This touched the heart of the Sky Goddess, and a single tear fell down from her eyes. Being the Goddess of the Mind and Logic, emotions are unusual to Oshtur. The tear from her eyes gave is what spawned Agamotto. She left and later instructed Agamotto to take the path of magic.
Oshtur also created a race of winged beings reminiscent of the biblical angels known as the Bird-Men of Akah Ma'at. Chthon later on whispered lies to the ears of Varuna, lord of the Bird-Men of Akah Ma'at and many other of his race, persuading them to become the Asura; judge, jury and executioner of man and other "lower races."
Those of Akah Ma'at who did not follow Varuna were lead by Saraswati, who was a great priestess to the Goddess of the Easter Star. Saraswati and her followers were filled with shame at the shadow that overtook the Asura. They vowed to shield all those who the Asura would harm and came to be known as the Seraphim.
Chthon once again caused evil and instigated a war between the Asura and the Seraphim. The war caused much destruction that Oshtur banished the Asura into another dimension. Till this day, the Asura still resides in the planes of Sephirot to this day. This epic tale of corruption of these winged beings perfectly reflects the story of Lucifer's rebellion against Heaven and his fall from grace.
During Oshtur's travel across the stars, she met up with Hoggoth, one of vastly powerful ancient mystical beings known as The Old Ones. The two of then with Oshtur's son Agamotto formed the eternal Vishanti, a trinity of aspects and beings which possess unimaginable power.
Since then, the Vishanti have protected the Earth dimension for eons from powerful beings such as Shuma-Gorath and Chthon, and created the office of the Sorcerer Supreme to help battle such threats.
Another interesting note, is that Oshtur appears to have strong favor for the bloodline of Ororo Munroe, known as the X-Men member Storm. For some unknown reason, since the dawn of Atlantis, this line of African women has been given distinguishing features of white hair, blue eyes, and powerful magic potential.
Oshtur is a vastly powerful cosmic entity capable of any feat imaginable. Magicians and sorcerers often claim her Omnipotence and often invokes the aid of her "Omnipotent Hands", but since she seeks aid from various sorcerers like Dr. Strange, she may not be truly Omnipotent, but more likely such title reflects her as a being of vast and infinite power. She also bestows her powers to the benevolent sorcerers who invoke them. The white magic Oshtur bestows on those faithful to her, is the equivalent of the dark magic Chthon bestows upon his followers.
Oshtur is also capable of projecting herself or at least her image across dimensions to Earth, even to human dreams and appearing to virtually anyone or anything. According to one of Doctor Strange's spells, she also hurled a lance known as "The Tower of Towers" suggesting the colossal size of one of her manifestations.
Oshtur is regularly depicted as a green or golden-skinned woman with hair that is either leaf-like, bald, or long and blue. She also has manifested in a corporeal form as a woman with white hair and draped in white clothes and celestial light, reminiscent of Storm herself.
The angelic/heavenly Oshtur serves as the opposing power against the demonic/hellish Chthon, whose very presence on Earth Dimension threatens the entire Universe. She is also responsible for the creation of the Book of the Vishanti, a tome of White Magic that serves as the opposing power to the Book of the Darkhold created by Chthon.
The Sword of Bone was Oshtur's contribution to the Four Cornerstones of Creation. The sword itself in made out of sharp, interlocking bones surrounded by a mystical blue flame and capable of slicing through any known substance. It must also be noted that the aura from the Sword of Bone is capable to damaging the Hulk himself.
Oshtur is known for her kindness and nobility. In fact, her Egyptian alias, Ma'at, worshiped by the powerful sorceress Ashake, is the Goddess of truth, law, order, and justice.
Oshtur's name was derived from the Greek words Eos which means "Dawn" and Ast'eri which means "Star". Her character is probably based on Ostara, the Goddess of the Dawn and the Spirit of Light. Her festival is known as The Feast of Eostre, whose worship was later absorbed into Christianity as the Christian Feast of the Annunciantion of the Virgin Mary (Lady Day) or Easter. Oshtur is associated with virginity or virgin birth, as her birth to Agamotto without procreation, and her being referred to as the Bird Goddess like how storks bring babies to new parents also symbolize this.