See also: Jan'Tep Magic
Also called familiars, such animals can be called and bonded to a mage (specifically a Jan'Tep mage) to strengthen their powers and act as companion and protector. But as the strength of a power animal bolsters that of their human, so bonding to a sick animal can cause a mage to die. It is for this reason that mages have a companion stay with them while they go into the trance required to call a familiar, to keep unwanted creatures from touching the mage. Shalla herself comes very close to such a fate.
At the beginning of book one, Kellen pretends that a passing falcon is his power animal, for they are the most revered of all familiars. Shalla, of course, is able to call one for herself, though it dies by the next morning.
Both Kellen and Reichis (who is vaguely considered a familiar) and Nephenia and Ishak share a special form of communication between them. Though Familiars understand one another and all humans clearly, the mages only comprehend their own animals.
After nearly dying in the desert, Reichis looses so much of himself that even Ishak has trouble understanding him, and his link with Kellen is completely severed until Diadera takes matters into her own hands.