Something the preview doesn't tell you about is the magic of the sixth family that left Salem. The preview offers five magic styles: Breath, Skin, Muscle, Blood and Bone. They each symbolize a certain kind of magic. But nothing hints at the magic of the sixth, forgotten (or lost or destroyed) family. That's got me thinking.
There is a pattern to the magic of the Five Families. Successively progressing deeper into the body. What comes beneath the bones? I came up with two answers: organs and the brain. Therefore, the sixth kind of magic could be either Organ Works or Brain Works. Organ Work doesn't sound that cool, so may be Entrail Work? Hm... Anyway, here is a short take on both works:
Organ Work: Messy things, hurtful things, knowledge and power from beyond space and time, to gaze too deeply is to invite madness. Things even witches were not meant to know. Aligned with deepest darkness and despair.
Brain Work: The magic of magic. The power to alter leylines and Places of Power. The crystal clarity of thought. The way to read and control thoughts. Aligned with time.
Interestingly, both types of magic would give the Five Families a reason to extinguish the sixth. Did they do it out of fear? Necessity? Envy? Or mixture of all three? Does the deed bind the Five Families together or will it rip them apart?