Cu Sidhe are the faerie dogs. Unlike the Cait Sidhe, each individual has two dog forms. The first is common to all Cu Sidhe, and is a "candy cane" colored sighthound- tall, white, with red paws, ears, and tail. This is the form most are born in. The second form is unique to each individual and looks like any other non-fae canine. Their human appearance features wolfish golden eyes, a squarish nose, and blonde hair with blood red streaks.
The Cu Sidhe have sharp senses and appear to have at least some skill in smelling the balance of blood even in human form. They are loyal and obedient, and eager to please. While intelligent, they 'prefer simplicity and joy to complexity and angst'. They historically enjoy fighting with the Cait Sidhe.
Tia, Madden's sister, currently incarcerated for her role in betraying the Yates family in the War of Silences