Mephastophilis is the devil that Faustus summons through his initial magical experiments. He is the same devil that was cast from paradise with his master Lucifer. In `Dr Faustus,' Marlowe creates Mephastophilis' personality from his own imagination, which causes Mephastophilis to be almost human at times. Mephastophilis is bound to Faustus because Faustus sold his soul to Lucifer for twenty-four years of Mephastophilis' service. During this time Mephastophilis sometimes openly despises Faustus' folly in disbelieving him, yet at other times Mephastophilis is like a companion or servant to Faustus as the scholars used to be.

These two aspects to Faustus' character can be shown through his appearance, actions and his language in particular. Mephastophilis is a terrifying devil in a human's eye and when Faustus first sees him he is disgusted by the sight of him as it is shown when he says:

"I charge thee to...