Walpurgisnacht to the symbolic one.
At the climax of SM Stirling's Drakon (New York, 2000), New York is blacked out as the single invading Draka fights about fifty human beings armed with futuristic weapons by her Samothracian opponent. One character rightly compares this event to "'Walpurgisnacht...'" (p. 364) Demons, or the next best thing, are loose and this could be the last night of human civilization or even of human life, the equivalent of the Final War on Earth/1.
The Draka, Gwen, has contacted the Domination timeline and spoken with the Archon who has appointed her Planetary Archon of Earth/2. Her human followers, traitors to their species, look forward to a good life, for them, under her rule. And I have not yet read to the end of the novel so I do not know the outcome.