A shadowbinder is a practitioner of magic who allegedly bind shadows to do their will. They possibly originate from Asshai, as the shadowbinders Melisandre and Quaithe come from the city near the Shadow Lands. R'hllor counts shadowbinders amongst his followers.
A Game of Thrones
A Clash of Kings
Stannis Baratheon enlists the aid of the red priestess and shadowbinder Melisandre. Daenerys meets Quaithe for the first time; the shadowbinder proceeds to give the young queen cryptic information during her journeys.