Magic is a force of nature. Supernatural perhaps, but still not beholden to concepts like good and evil or right and wrong. Like any tool, magic in the wrong hands can be deadly. Anyone can use magic for ill or good, with one exception. Necromancy is a corruption of life, death, and magic itself. As such, other magic users universally hunt down and destroy necromancers.
Among arcanists who weather the bleak times of no magic, most avoid the temptation to employ dark rituals. Those who do are human in name only. Power in the bleak times comes from the only consistent source of magic, human sacrifice. Foul atrocities like murder and torture gave a handful of arcanists ill-gotten power over the past six thousand years.
Modern magic users in the world of Fantastic America have little or no idea how magic works. Yet even modern arcanists who drew power from murder lost all understanding from the last magical age. Only a few desperate and deranged would-be magicians sought out the lone source of magical knowledge still accessible.
As necromancy is a great corruptor, the secretive Mistress of Shadows is the greatest corruptor of all. She alone has dared to break the ancient covenants that bar other immortals from interfering in mortal affairs. The few who have won her favor have perpetrated the worst kinds of torture, bloody rituals, and depravity. Their mistress’s rewards made them powerful, defied aging, and staved off death itself, for a time.
Magic users of the modern world have no idea of the forces unleashed by the return of magic. Monsters not seen in thousands of years roam the Earth. Unsettling eruptions of magic change familiar locations into places of power. Meanwhile, intelligences older than our oldest ancestors wait for their moment to break the last bonds that restrain them.