St. John with the chalice of snakes
The Emperor wanted St. John dead and thus gave him a cup of poison. Upon receiving the cup, the liquid miraculously turned into snakes, thwarting the Emperor's plot.
St. John writing next to his symbol the eagle
St. John on Patmos with demon stealing his writing instruments
Demons often show up with malicious grins and engaged in devious activities. Here the demon tries to steal St. John's writing implements. In many cases, readers fearing the demonic images would rub out their distinguishing features in order to lessen their threats (this demon may appear faint either from the age of the manuscript or from rubbing).