August 15 Ritual Date

documentary and testimonial (multi-source) very high (four+ independent sources) Multiple sources, multiple sessions

Description

Midnight, 15 August 1814 — Feast of the Assumption. The scheduled performance of Segment V of the Grand Canticle by the Brotherhood_of_the_Open_Measure at the Sealed_Anatomical_Theatre beneath the University_of_Vienna.

The ritual deadline is absolute. The Choir’s ritual architecture requires simultaneous performance across the eight ritual sites (see Campaign_Overview_Updated), and this date is locked by the celestial and liturgical calendar.
The Feast of the Assumption is one of the most significant dates in the Catholic calendar — a public holiday in Vienna, when the city is distracted by religious observance and diplomatic social events. This provides cover for the ritual.
If not disrupted by midnight, the Vienna cell’s Segment V completes successfully and contributes to the Grand Canticle’s “5 of 8” threshold.
If disrupted at any point before midnight, the Brotherhood loses its Vienna contribution. Whether that is operationally survivable for the cell depends on whether they can reconstitute the Engine or re-obtain a trained voice like Anna’s. Both are unlikely in any reasonable timeframe.

This clue is multi-source and therefore highly reliable. Sources in approximate order of discovery:

Chapter 2, Lyon: Savarin’s correspondence, recovered post-ritual, includes a letter from Herzfeld in Vienna mentioning August 15 and the “Brotherhood of the Open Measure”
Chapter 3, Session 1 (August 3): Herzfeld’s letter (carried from Lyon) is re-examined for Vienna planning. August 15 confirmed as the target date.
Chapter 3, Session 2 (August 4–5): Brenner’s pre-death testimony — the ritual is August 15 at midnight.
Chapter 3, Session 5 (August 7): Trautmannsdorff’s confession confirms August 15 midnight, Feast of the Assumption.
Chapter 3, Session 8 (August 8): Honoria reconfirms the date at the masquerade with updated intel from Munich channels.

Operational anchor: every Chapter 3 plan is paced against this deadline. As of the end of Session 8, there are 6 days remaining (5 once 9 August ends).
Related clues: A=432 Hz — The Engine Resonance, The 5 of 8 Requirement, Der Kantor / Munich Coordination
Counter-operations: disrupting the Engine, rescuing the ritual’s trained voice (Anna — done), assassinating Herzfeld, sabotaging the theatre’s acoustics, or raiding the theatre before the ritual begins

Schedules Harmonic Engine — The Engine is scheduled to perform at midnight August 15
Deadline for Albin Herzfeld — Herzfeld must have the Engine operational by midnight August 15
Locates event at Sealed Anatomical Theatre — Ritual location beneath the University of Vienna