Isis (Egyptian Aset) is defined by an act of devotion. When her husband and brother Osiris is murdered and dismembered by their brother Seth, it is Isis who searches out the scattered pieces of his body, binds them together, and by her magic revives him long enough to conceive their son Horus. She is thus the model of the grieving and faithful wife, the protective mother, and the mistress of heka, Egyptian ritual power, all at once. A well-known myth even has her win Ra's secret name, and with it a share of the sun-god's own power, by cunning.
The fullest connected narrative of this story survives, ironically, in Greek: Plutarch's On Isis and Osiris, written centuries later, gathers a version that the fragmentary Egyptian sources only allude to. The Egyptian texts assume the story rather than tell it whole, so the historian reads them alongside Plutarch while remembering that he was an outsider systematising material for a Greek audience.
Her devotion had a practical edge for every Egyptian: as the mother who hid and healed the infant Horus in the marshes, Isis was invoked in spells to protect children and cure the bites and fevers that threatened them.