The Changewinds (Baen Science Fiction)

The Changewinds blow from the Seat of Probability across the worlds that they themselves created, at once random and consistent, obeying the rules of their own strange spectral meteorology. Most of the universes the Winds have made exist separately from one another in time and space, but close to the Seat of Probability they are more densely packed, and one may walk from one to the other and not realise it until it is too late...For countless centuries the Ahkbreed sorcerers have dreamed of the ultimate power - control and direction of the Changewinds themselves, a power that would truly make them gods over all universes everywhere. And for centuries those who pay tribute to the Ahkbreed have dreamed of a deliverer. Now two brave young women from Earth have found themselves caught up in the fury of the Changewinds. They themselves will be transformed. But, in the process, they will change everything.