Calling on Dragons by Patricia C. Wrede, 1993.

This is the third book in the Enchanted Forest Chronicles. Cimorene is now married to Mendanbar and expecting their first child.

Morwen, a witch living in the Enchanted Forest, realizes that something strange is going on when she encounters a rabbit that is more than six feet tall. The rabbit, called Killer, has no idea how he managed to grow so big. It just happened suddenly that morning while he was eating some clover. Morwen goes to investigate the clover patch in the hopes of finding what might be responsible for the change. She discovers a wizard’s staff nearby, which is never a good sign.

She contacts King Mendanbar, Queen Cimorene, and her friend Telemain, a magical theoretician. Part of what they discover is that one of the wizards has shrunk himself in size. Mendanbar also discovers that someone has stolen the sword that he uses to control the threads of magic in the Enchanted Forest. The sword helps to maintain the protective spell around the Enchanted Forest that keeps wizards out. If the wizards have it, they may be able to enter the forest and soak up its magic. Mendanbar wants to go with the others to get it back, but Telemain points out that he can’t because he’s the other main focus of the protective spell; if he leaves the forest, it will be completely vulnerable. Even worse, they don’t have much time to retrieve the sword because whenever it’s outside of the Enchanted Forest, it leaks magic. Although Mendanbar doesn’t want to let Cimorene go on the mission to retrieve the sword while she’s pregnant, he has to let her go with the others. Before the book is over, Killer, who accompanies them on their mission, changes from a giant rabbit in to a flying blue donkey.

Among the fairy tale parodies that the characters encounter on their journey are a farmer named MacDonald (E-I-E-I-O) and a sorceress named Rachel who lives in a tower that can only be entered via a chair which Rachel lowers to bring people up (“Rachel! Rachel, send down the chair”). They keep in touch with Mendanbar in the castle using a magic mirror (“Mirror, mirror on the wall, I would like to make a call.”), until, for some reason, they are unable to reach him.

They are able to retrieve the magic sword, but the wizards capture Mendanbar and seal him inside his castle, trapped in a transportation spell to keep him safe yet contained. They don’t want to kill him because the Enchanted Forest would be plunged into chaos by his death, and they can’t keep him prisoner in a normal way because his friends would rescue him. Cimorene and the others know that the sword has the power to break through the shield spell on the castle, but the problem is that only a member of the royal family can wield it to do so. The sword allows Cimorene to carry it because she is Mendanbar’s wife, but only a blood relative can use the sword to break the spell . . . which mean that they have to wait for Cimorene’s baby to be born and become old enough to do it.

Although I like this series and think it’s a lot of fun, I’m not really fond of the last two books because of Mendanbar’s years of imprisonment. He’s okay when they finally get to him, but I still don’t like it. The ending of this book leaves things hanging until the fourth book.

This book is currently available online through Internet Archive.