With unrelenting force of will, Onewa commanded the stone to reject that which did not belong.  He could sense that the rock had been interwoven with the substance of Matau and there would be no way to rip the Toa free.  The rock would have to set him free.  Painfully, inch by inch, he felt the stone retreat. Driven back by the power of the Toa Metru, it released its hold at last on Matau.

Maze of Shadows, Greg Farshtey, p 46