At first, it’s a completely mystifying image: Why do medieval manuscripts show knights fighting snails? These marginal illustrations are surprisingly common (you can peruse a few colorful, snail-filled examples courtesy of Yale’s library and the British Library). But even though it seems like there’s no possible explanation for all that knight-on-snail combat, the above video shows some of the top theories.

The most convincing argument comes from medieval scholar Lillian Randall’s 1962 essay “The Snail in Gothic Marginal Warfare” (an argument echoed in Michael Camille’s book about marginal art, available here). Randall theorizes that these snails began as representation of the Lombards, a maligned group that rose to prominence as lenders in the late 1200s. From that original caricature, snails and knights became a trope in medieval marginal art.

As the video shows, medieval marginal art was an unusual playground for surreal and fantastic drawings. Seeing them now shows the character and whimsy of the scribes that set them loose on the page.