There are several characters who represent evil at Walpurgis Night (or Walpurgisnacht) in Goethe's Faust.
Walpurgis Night is:
[t]he 17th century German tradition of a meeting of sorcerers and witches on May Day is influenced by the descriptions of Witches' Sabbaths in 15th and 16th century literature.
One evil character is mentioned when they arrive:
...the climactic performance on the summit [was] presided over by "Herr Urian"...a name for the Devil...
Goethe lampoons a literary enemy, Friedrich Nicolai, the old warhorse of the German Enlightenment.
Goethe may see Nicolai as "evil" because of Nicolai's involvement with Allgemeine deutsche Bibliothek:
This...periodical served as the organ of the so-called popular philosophers, who warred against authority in religion and against what they conceived to be extravagance in literature.
Goethe's dislike for the man stems from Nicolai's inability to understand Goethe and other writers of the time.
Faust dances with a young witch but when a red mouse crawls out of her mouth, he finds he is not that interested. Mephisto warns Faust to look away from the "Gorgon," (in Greek mythology, one of three beautiful women with hair of writhing snakes who Perseus faces—if looking directly upon any of them, a person would be turned to stone).
Traditionally, while two of the Gorgons were immortal, Stheno and Euryale, their sister Medusa was not, and was slain by the mythical hero Perseus.
Even with the warnings, Faust looks at the Gorgon; Mephisto tells Faust that this woman is Adam's first wife, Lilith.
In the Jewish faith:
[It is] suggested that Eve and the woman of the first account were two separate individuals, the first being identified as Lilith, a figure elsewhere described as a night demon.
Lilith...is a character in Jewish mythology, found earliest in the Babylonian Talmud, which is generally thought to be related to a class of female demons Līlīṯu in Mesopotamian texts.
They see a variety of witches and wizards; there is also a witch that sells or peddles her wares: sounding like things from Macbeth, there are items used in murders, poisons, etc.
This is a night when all spirits are allowed to move freely on the earth.