A Word as Bond is a magical contract used to seal the terms of a pact.
Accompanied by a sigil drawn onto a piece of paper, the intended parties then draw blood and add it to the sigil, activating it. Then, they place the base of their thumbs onto the sigil, branding the spell onto themselves and sealing the bond. A Word as Bond spell is believed to be unbreakable. Even Alice as a Niffin stated as much, and Brakebills had no information on how to alter or break a Word as Bond spell. However loopholes can be exploited within the exact rules of the Bond.
Julia Wicker and Martin Chatwin
Following the Physical Kids' attempt to assassinate Martin Chatwin in Fillory, Julia Wicker and Martin formed a Word as Bond under the terms that, in exchange for having saved his life, Martin would help her track and kill Reynard the Fox.
Quentin Coldwater and Alice Quinn
Following her transformation into a Niffin, Alice Quinn was trapped by Quentin Coldwater's Cacodemon in the seal on his back. After Quentin discovered Alice hadn't been destroyed, he allowed Alice to control his body only if she agreed to a Word as Bond that limited her actions.