Maw spewing fire, harsh scales, menacing eyes, crests and tails. That is the image that comes to mind when we think of the dragon. This imaginary animal, the result of a huge accumulation of written and iconographic sources developed over time, was of constant interest in the Middle Ages. Its literate culture revisited its figure with great assiduity through its allegorical, symbolic, pedagogical and persuasive facets in lectio and liturgy. This book proposes to investigate the various symbolic and practical functions of the dragon within illuminated codices produced in Hispano-Christian monasteries between the twelfth century and the beginning of the thirteenth. The Romanesque dragontine image managed to firmly establish itself as a demonic animalistic prototype in the medieval visual culture of that time. Likewise, its diffusion in the Iberian Peninsula was accompanied by the impact of Style 1200, by the circulation of foreign bestiaries and by a more empirical view of nature. The dragon designs began to have a greater effectiveness and pictorial impact and marked a considerable imprint in Hispanic territory. Both in central miniatures as in capital letters and in marginalia, the image of the dragon began to multiply in the Hispanic manuscripts of those centuries and operated under different strategies for its reading. Their sleek and ductile bodies managed to adapt to the different graphic formats of the folios, while their monstrous faces forged an important quota of visual appeal. Thus, miniaturists frequented more and more versatile graphic repertoires of dragons in direct relation to the different uses and functions that these could awaken in the eyes of the intrepid monks who read these manuscripts daily.