Astrid Mordo is the result of an incestial relationship between Baron Mordo and his niece Lilia Calderu. She was born months following the end of that relationship. Nothing further is known of her early life.
Astrid has obviously received magical training. She employs demons as witches' familiars, teleports at will, employs mystic daggers and magic bolts as weaponry. Her most notable ability allows her to drain the magical powers of other beings into herself. Adding them to her own.
Astrid Mordo was first seen in a plot involving the approaching death of her father. Baron Mordo was dying of cancer and was willing to accept death. He mentally contacted Doctor Strange to converse for the final time. Astrid used that mental contact to transfer the cancer from the body of her father to that of Strange. She then attacked the former monastery of the Ancient One, where her father had retired to live his final days.
She abducted her surprised father, Hamir and other monks. Transporting them to Castle Mordo. She later send one of her demons to Nebraska. The demon was able to deliver Doctor Strange, weakened from the cancer, at her feet. Strange expected this to be a plot by his archenemy. He was astonished to find out that a novice sorceress had accomplished this.
Astrid proceeded to drain the monks from their magic energies. Preparing herself to slay Strange. But Karl used a mystic shield to protect Strange. Claiming the right to kill Stephen for himself. Astrid was convinced to give her father this joy.
She hadn't counted on Karl turning on her. He approached Strange and transfered the cancer back to his own body. Karl wanted to stop his daughter but was reluctant to hurt her. Tasking Strange with defeating her. Astrid found herself facing a healthy and aggressive Strange. She tried using the fears of Strange agaist him. Calling on the demons who had plagued the childhood dreams of Strange and to those who haunted his youth. But Strange had long ceased being afraid of bogeymen.
Astrid then teleported Amanda and Jessica Payne in the battlefield. Threatening to slay them if Strange failed to surrender. Strange ceased attacking. But Astrid was then felled by a surprise attack by her own father. He rendered her comatose and transported her body to another plane of existence. Then claimed for himself a fate that his daughter had foolishly denied him: a dignified death.
Astrid is presumably still comatose.