He is the serpent who tempts Eve to eat the forbidden fruit, the fallen angel who rebelled against God, the Dragon, Beelzebub, the Father of Lies, Lucifer, Satan, the Prince of Darkness.
A giant beast, he stood frozen to the waist in a lake of ice in Dante's Divine Commedy, chewed on the damned in early Renaissance paintings, made a pact with Faust as Mephistopheles, rode a tank and "held a general's rank when the blitzkrieg raged and the bodies stank" -- if you trust the Rolling Stones.
A popular icon in the past, the devil appears to be alive and kicking also in Pope Francis' modernizing church.
The pontiff has alluded to him ever since his first homily as Pope, when he boldly quoted the French author Léon Bloy: "Anyone who does not pray to the Lord prays to the devil."
This week, speaking at a massive gathering in Rome's Olympic Stadium, Francis warned about the "devil wanting to destroy the family" and told married couples to raise children rather than owning pets. He ended his much-criticized remarks by portraying a life of loneliness and bitterness to those who love pets like they would children.
"Families face attacks from the devil because Jesus grows in parent's love and children’s lives," he said.
But who, or what, is the devil?
A Literal Threat
Far from being a metaphor of evil, Satan appears to be a real, supernatural hellish force in Pope Francis’ almost obsessive remarks. Such a crude view has, however, changed several times through the centuries.
For example, in the Old Testament, Satan is not the devil seen in horror movies.
"He is a loyal servant of God, and a relatively minor figure," Darren Oldridge, a specialist in early modern religious history and the author of several books on the devil, told Discovery News.
"The devil is far more prominent in the New Testament, and here he is emphatically the enemy of God and goodness," he said.
Often depicted as a rapacious monster through the Middle Ages, the devil was increasingly viewed as an invisible spirit of temptation during the 16th-century Protestant Reformation initiated by Martin Luther and John Calvin.
"More recently, some liberal Christians have understood Satan in metaphorical terms. But he remains a real presence among evangelical Protestants and Catholic traditionalists," Oldridge said.
The devil was indeed a real presence for Paul VI, Pope from 1963 to 1978. Back in 1972, he famously warned against the very physical "smoke of Satan" in the Church.
In another 1972 address, Paul VI called the devil "a living, spiritual being that is perverted and that perverts others."
"It is a terrible reality, mysterious and frightening," he concluded.
Although John Paul II agreed “the devil is still alive and at work,” at a general audience in 1999 he smoothed over the strict, traditional Christian teachings by denying heaven and hell as physical places.
Rather than a physical place, John Paul II declared: “Hell is the state of those who freely and definitively separate themselves from God.”
However, Francis’s teachings on the devil appear to be more in line with Paul VI’s old-school interpretations of Satan.
"Some of you might argue: ‘Father, how old fashioned you are to speak about the devil in the 21st century," Francis recently said during a Mass at his Santa Marta residence. "But the devil is present! The devil is here... we mustn’t be naive."