In the University of Oxford’s Bodleian Library, amid a vast collection of medieval texts, there is a manuscript known as The Ashmole Bestiary. It’s a particularly lavish example of one of the most popular kinds of texts in the European Middle Ages: a book of beasts, describing animals—real and imagined—and their meanings within the time’s Christian belief system.

In one of the illustrations, a fox pretends to be dead in order to attract birds; once they are close enough, it leaps to life to devour them. In another, a spotted panther attacks its only enemy—the dragon. In yet another, a lion breathes life into its dead, three-day-old cubs. These were more than mere illustrations; they were Christian allegories. According to the new edition of The Grand Medieval Bestiary—a 620-page behemoth by Christian Heck and Rémy Cordonnier, devoted to medieval creatures great and small—the fox was commonly portrayed as untrustworthy, and ensnared birds the way the devil traps sinners. The panther symbolized Christ, with the ultimate serpent—the dragon—as the devil. The life-giving lion was, of course, related to the resurrection.

A Weasel Combating a Basilisk, Folio 79, Bestiary of the Second Family, also known as The Ashmole Beastiary, Peterborough Abbey or Canterbury Abbey, c. 1200–10. Bodleian Library, Oxford, MS Ashmole 1511

The blueprint for medieval bestiaries arose long before the Middle Ages. The Greek text Physiologus, written in Alexandria sometime between the second and fourth centuries, linked particular animals to Christian morals and stories. In the seventh century, Isidore of Seville produced his 20-volume Etymologies, an encyclopedic tome on a range of subjects, from mathematics to agriculture to furnishings. Book 12 related to animals, but without the Christian moralizing. Instead, it focused on how the etymology of animals’ names related to their characteristics.

By the 12th and 13th centuries, when The Ashmole Bestiary is believed to have been written, bestiaries had become particularly popular in England. They also had broad appeal because even the illiterate could understand the stories behind the illustrations.

Ulysses and the Sirens, from Le Roman de Troie, Paris, 1341. Bibliothèque Nationale de France, Paris, MS fr. 78

Animals appeared in medieval texts beyond bestiaries as well. Marginalia, the doodles and drawings on the edges of manuscripts of all sorts, commonly featured animals. (These drawings are not the only embellishments in medieval manuscripts, either. Some texts contain delicate embroidered patches in the parchment, itself made from animal skin.) Animals also featured in art, tapestries, heraldry, and jewelry, and continued to carry the meaning and symbolism that had long been ascribed to them.

As The Grand Medieval Bestiary points out, “Whether they are faithful servants and benevolent companions, subjects of a humorous fable or parody, wild animals that represent danger or evil, or strange creatures from afar, real or imaginary, their place on these pages is as important as the place accorded to them in the life and culture of the period.”

Atlas Obscura has a selection of images of medieval beasties from the compendium.

Alexander the Great Borne Aloft by Griffins, Folio 257v, Livre des Conquestes et Faits d’Alexandre, France, mid-15th century. Musée du Petit-Palais, Paris, MS L. Dut. 456

An Ostrich Saving Its Young with the Blood of an Asp, from Miroir de l’Humaine Salvation, France, 15th century. Musée Condé, Chantilly, MS 139

Wild Fauna, Including a Giraffe, Folio 3, Verses on Events from the History of Sicily in the Time of Frederick II, c. 1330–40. British Library, London, MS Add. 28841

Leviathan Ridden by the Devil, Folio 49, Liber Floridus, 1460. Koninklijke Bibliotheek, The Hague, MS 72

The Giant Snails of the Island of Calonak, Folio 4v, Les Secrets de l’Histoire Naturelle, c. 1428. Bibliothèque Nationale de France, Paris, MS fr. 1379