From Monsignor Pope.
Spy Wednesday Annual Reflection on the Sins and Shortcomings of the Clergy
This fresco (below), by Giotto di Bondone, is from the Life of Christ series at the Arena Chapel (Cappella Scrovegni) in Padua, Italy. Giotto created it between 1304-06.
In this scene (number 28 in the series), Judas (who is holding a money bag) has made a deal with the religious leaders to betray his friend, Jesus. Note the figure in black, which Giotto has painted behind Judas. It is his representation of Satan. http://www.awesomestories.com/assets/judas-betrayal-fresco-by-giotto