Bastard's girls

The Bastard's girls are a pack of vicious dogs bred by Ramsay Snow.

In the books
In the A Song of Ice and Fire novels, the "Bastard's girls" are how Theon Greyjoy refers to Ramsay Snow's pack of feral dogs.''

Ramsay uses the hounds to partake in his sick practice of releasing women naked into the Bolton Forests where he hunts them for sport after giving them a days head start. The pack is made up of all vicious, mean tempered bitches. The dogs are looked after by the kennelmaster Ben Bones of the Dreadfort who under Ramsay's instructions also trained them to kill wolves.

Those women he hunts that give him good sport are given a quick death (after being raped) and in "honor" of the hunt, Ramsay names a new bitch pup after the woman. Those women that do not give him good sport are not given a quick death but are flayed alive and do not get a dog named after them. His current pack consists of...
 * Grey Jeyne
 * Helicent
 * Jez
 * Alison
 * Kyra
 * Maude
 * Red Jeyne
 * Sara
 * Willow

Behind the scenes
Iwan Rheon confirmed their appearance in the TV series when he tweeted a set photo of them in their kennel.