The second hidden guild Milk masters, next door to the calligraphy guild inside Club Vanquisher.
The Cartography Guild sits next door to the Calligraphy Guild inside Club Vanquisher, and Milk is guildmaster of both. Like its neighbor, its door is hidden, and nobody ever enters — a fact Milk cites when explaining why she has never bothered concealing her stacked newsletters. As a Cartographer by class, Milk's cartography work is presumably what her Indentureship counts: she will not be freed until her services are used at least 333 times in the dungeon, and so far they have been used six times.
Her Milk's Map of the club's secret entrances and exits is the guild's most valuable product, and she offers it to Miriam and Prepotente under the pretense of being robbed.
A guildhall behind a hidden door in the club wall, adjacent to the calligraphy guild.
Milk's other guild, and the source of the maps that can get crawlers out of the club unseen.