Cassandra Nova began life at the same time as Charles Xavier. Conceived without a body, Cassandra improvised one by copying Xavier's DNA to make her own body, effectively becoming his twin sister. She grew with her brother until the time when Charles sensed her monstrous thoughts. Charles attempted to kill the creature, resulting in its physical body being stillborn. Despite this, the creature survived as chaotic cellular matter and clung to a sewer wall for decades, rebuilding its physical form and perfecting its effort to mimic human traits. During this time, she grew convinced that the womb in which she had fought Charles and the universe she now inhabited were one and the same, a universe in which only she and Charles were real, and that her purpose was to destroy every illusion Charles held dear: his dream, his X-Men and his beloved Lilandra.  Jean Grey later discovered that Cassandra Nova is the mummudrai (from a Shi'ar legend, meaning opposite) of Charles Xavier. "Legend says each of us faces our own personal mummudrai in the womb, shortly before birth - it is our first experience of the alien, the other, the different". In reality, the mummudrai are a parasitic species born bodiless on the astral plane, and it was only through becoming entangled with Charles Xavier's developing telepathic mind that Cassandra Nova created a body for herself