Berlioz, "Bloksberg scene" in Goethe's Faust

This reference, which puzzled me, appears on p. 65 of Berlioz's book, "A Critical Study of Beethoven's symphonies."
Here is a site that offers an explanation:

http://www.harryprice.co.uk/Famous%20Cases/brockenbyharryprice.htm

esp.

Goethe made an intensive study of magic and witchcraft, and his classical scene of the Walpurgisnacht in Faust has done much to immortalise his 'divine comedy'. That Goethe studied the original of the Bloksberg Tryst is almost certain, as several correspondences between the old MS. and the Walpurgisnacht are apparent.
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(The Walpurgisnacht scene is a famous depiction of a sexual orgy, staged to tempt Faust--the only thing I understood in a performance of Faust, Part 1, that I saw years ago in Austria. Below is a short description.)
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http://www.catholiceducation.org/articles/arts/al0117.html

The temptations the devil offers Faust are three: gluttony, lust, and power. The carousing with students in Auerbach's pub in Leipzig . . . a traditional Faustus motif Goethe retained . . . only bores Faust, so Mephistopheles realizes he must resort to stronger stuff: sex. Here too there are three facets. Faust is tempted first with Gretchen, who represents the epitome of pure, innocent German maidenhood, then with raw lust at its most orgiastic in the Walpurgisnacht scene, when the devil holds his annual conclave with all his witches . . . a motif Goethe borrows from German folklore . . . and lastly with Helen of Troy, the epitome of classical beauty, whose shade Faust conjures up from Hades. Faust rejects the debauch with the witches; he is not so crude as to be gotten at by such means. But with Gretchen and Helen it is a different story, and Mephisto almost succeeds. "Almost" because it is not only lust that consumes Faust.