Calling on Dragons is a young adult fantasy novel by Patricia C. Wrede, third in the Enchanted Forest Chronicles.
Morwen, a witch who lives in the Enchanted Forest, is having trouble with people who believe that magic should follow traditional forms, specifically one Arona Michealear Grinogion Vamist.
Morwen and Telemain immediately go to the castle of King Mendanbar and Queen Cimorene, who is pregnant.
The next morning, again with Brandel's mirror, they find that the sword is not at the headquarters of the Society of Wizards as they assumed, but at the house of Vamist.
Morwen and Telemain move the spells on Killer onto Vamist, returning the rabbit to his natural form.
[2] Brian E. Wilson of the School Library Journal wrote that it "emerges as a fluffy romp that goes down easy, pleasing fans of the fractured fairytale genre", although he opined that Wrede "does stretch some jokes too thin".