Early Middle Ages
Translation of the work of John of Damascus provided West with some information about Muhammad's life but "was nearly always used abusively." Another influential source was the “Letters of a Saracen” written by an Oriental Christian and translated into Latin from Arabic. From the 9th century onwards, highly negative biographies of Muhammad were written in Latin.

West also gained some knowledge of Muhammad through the Mozarabs of Spain in the 11th century. In 12th century, the Qur'an was ordered to be translated into Latin so that its teaching could be refuted by Christian scholars.

Middle Ages
The medieval scholars and churchmen held that Islam was the work of Muhammad who in turn was inspired by Satan. Fantastic legends and fables emerged. For example, in order to show that Muhammad was the anti-Christ, it was asserted that Muhammad died not in the year 632 but in the year 666 - the number of the Beast. A verbal expression of Christian contempt for Islam was expressed in turning his name from Muhammad to Mahound, the "devil incarnate".

Muhammad was frequently calumnized and made a subject of ridiculous legends taught by crusading preachers to stir up hate against Muslims as fact, and usually confirmed to pious Christians that Muhammad had come to a bad end. According to one version after falling into a drunken stupor he had been eaten by a herd of swine, and this was ascribed to the reason why Muslims proscribed consumption of liquor and pork. Leggenda di Maometto is an example of those in which he is taught from childhood the black arts by a heretical Christian villain who escaped imprisonment by the Church to Arabia and set up a false religion by selectively choosing and perverting text from the Bible and the Old Testament to set up Islam. It also ascribed the Muslim holiday of Friday "dies veneris" (day of Venus) vs. the Jewish (Saturday) and the Christian (Sunday) to his followers depravity and reflected in their multiplicity of wives. During the Middle Ages, especially in places where there was frequent Christian-Muslim conflict, it was popular to depict Muhammad being tortured by the demons in Hell. One such example is in Dante's The Divine Comedy in which Muhammad is in the ninth ditch of the eighth circle of hell, the realm for those who have caused schism. One common allegation laid against Muhammad was that he was an impostor, who to satisfy his ambition and his lust propagated religious teachings which he himself knew to be false. At one point Muhammad was transformed into Mahound, the prince of darkness. A somewhat different interpretation appears in the 13th century Estoire del Saint Grail, the first book in the vast Arthurian cycle, the Lancelot-Grail. In describing the travels of Joseph of Arimathea, keeper of the Holy Grail, the author says most residents of the Middle East were pagans until the coming Muhammad, shown here as a true prophet sent by God to bring Christianity to the region. This failed when Muhammad's pride caused him to alter God's wishes, thereby deceiving his followers. Nevertheless, Muhammad's religion is portrayed as greatly superior to paganism.

Some Christians believed Muslims worshipped Muhammad, while others simply believed he was a Christian heretic.Still other medieval European literature often referred to Muslims as "pagans", or by sobriquets such as the paynim foe. These depictions such as those in the Song of Roland represent Muslims worshipping Muhammad (spelt e.g. 'Mahom' and 'Mahumet') as a god, and depict them worshipping various deities in the form of "idols", ranging from Apollo to Lucifer, but ascribing to them a chief deity known as "Termagant". John of Damascus coined the pejorative phrase "false prophet". and Alvarus of Cordoba proclaimed him the Anti-Christ in the 9th century. The number of the beast "666" was used to represent the period of time Muslims would hold sway of the land. In the 12th century Peter the Venerable saw him as the precursor to the Anti-Christ, and successor of Arius.When the Knights Templar were being tried for heresy reference was often made to their worship of a demon Baphomet, which was notable by implication for its similarity to the common rendition of Muhammad's name used by Christian writers of the time, Mahomet. All these and other variations on the theme were all set in the "temper of the times" of what was seen as an Muslim-Christian conflict as Medieval Europe was building a concept of "the great enemy" in the wake of the quickfire success of the Muslims through a series of conquests shortly after the fall of the Western Roman Empire, as well as the lack of real information in the West of the mysterious east.

There are accusations that the Knights Templar worshipped an idol named Baphomet. The etymology of this idol is questioned, and some speculate that it is a variation of a deformation of the Latinised name of Muhammad.