Summarizing the results of his ground-breaking study of the influence of Wagner's The Ring of the Nibelung on Nietzsche's Thus Spoke Zarathustra, Roger Hollinrake writes:

As Hollinrake observes further, Nietzsche's most pointed allusions, in the climactic scenes of Part III of Zarathustra, refer to the equally climactic scenes of Wagner's Ring in its third cycle, Siegfried. This is why Hollinrake suggests that Siegfried is “the germinal cell from which Zarathustra grows” (1982, p. 103).

Surprisingly, however, Hollinrake fails to notice Nietzsche's allusions in Part III of Zarathustra to those key scenes in Act II of Siegfried where the fearless hero kills Fafner and Mime (1982, pp. 80–82). These allusions can be found in the vision-riddle presented by Zarathustra at the start of Part III and fulfilled by the narrative at the end of Part III. In this vision-riddle, Zarathustra courageously overcomes his most abysmal thought and his archenemy the spirit of gravity. The awakened most abysmal thought appears to Zarathustra just as the awakened depth-dwelling Fafner appears to Siegfried – in the shape of a monstrous, toothed serpent.