The Taken are foxes that have had their will taken from them. Thus the name, The Taken. These foxes only follow orders from the Narral or from the Mage himself. They bear a mark on their forleg. Isla describes the mark to be like a broken rose.
How they came to be Edit
It started with the Mage, later revealed to be Keeveny. Keeveny is the Elder that is the master of pleaching, a foxcraft that is very dangerous to practice. Keeveny wanted to test the limits of pleaching. He captured free foxes and pleached them. Later on, Keeveny decided (for some odd reason) that he should bring back The White Fox. He kept on capturing free foxes, and with the help of the Narral, created an army of Taken.