Seven there were at the beginning, and Seven towers there were as well. Each took one of the stones to a location of their choosing, and planted the tower there, hoping that their choice would help safeguard these bastions of magic and enlightenment. With the towers in place, each sorcerer took their time recruiting other Talented individuals to help run it, and they in turn took apprentices, and so on. Eventually, whenever the time was right, each of the Seven vacated their positions at the Towers and left to explore beyond what they’d known before, furthering their own masteries of the Art.
One by one the world forgot about them and their deeds, and they only survived in legend. No one truly knows what happened to any of them, save possibly any others of the Seven… if even any survive today. What we do know, is that of the original seven towers, only three exist today.