Shadowbinders are a type of sorcerer, said to hail from Asshai. They are practised in various skills involving the binding of shadows to do their will. R'hllor counts shadowbinders amongst his followers.
A Game of Thrones[]
Eddard Stark hears reports that Stannis Baratheon has allied with a shadowbinder from Asshai, but is unclear about the report's accuracy or what it means.
A Clash of Kings[]
Stannis's shadowbinder ally is revealed to be Melisandre. The reason for the name is revealed when she draws on Stannis's life force to create two shadow creatures, one to slay his brother Renly and the other to kill Ser Courtney Penrose and secure the capitulation of Storm's End.
A Storm of Swords[]
Melisandre tells the captive Ser Davos Seaworth that creating shadows is hard work, being extremely taxing on the person whose life force is being used to create them. Having created two from Stannis already, she could not create a third without it killing him. She suggests Davos could make the sacrifice instead, but he refuses her.