Home of Magic

Long ago, during the period that led to the War in Heaven, a ancient AI known as the godmind decided to make a place to house his son during offtime between missions to keep primitive worlds in line with the great experment. (To keep them primitive.) What he could not see was his son's betrayal, which occurred during the demiplane's formation. At that point it was halted. Later, when the godmind decided to have a daughter, but not just any - he would form her body from magical energies. She would fight his betrayer of a son over the fates of the one hundred and one worlds (terraformed) in the sector.

which he had a abundance of. The plane would form based on who controlled how many of each system's stations were controlled by which of his children.