"Piergeiron"

Just who was sitting in Box 2 that night?

Was wearing clothing very similar to Stolen costumes.

Spotted at Lightsinger Theater on the evening of 13 Marpenoth, less than a day after Galvin Barnabas was found murdered.

It's safe to assume "Piergeiron" isn't their real name. Piergeiron the Paladinson was Open Lord of Waterdeep for most of the 1300s, before the Spellplague (see History: The Spellplague). Since Lightsinger Theater is a common place to send covert messages, it's probably meaningful.

Presumably, Piergeiron is affiliated either with the House of the Dark Blade or with one of their allies.