Architect Houston's lair beside his throne room, the only Madness stronghold nobody has ever infiltrated.
Arief explains that Houston's lair next to the throne room is what The Madness call the Operating Theater, and that nobody has managed to get into it. When Donut asks whether the Viceroy Juice Box decapitated at the pre-production meeting was Architect Houston himself, Arief corrects her: that was one of Houston's surgeons.
When Carl asks how much the awakened NPCs managed to sabotage, Arief says they bloodied every enemy encampment a little and got inside the inner circle of all of them at least once — except the Naga, of course, and except the Madness's Operating Theater. It stands, alongside the naga inner sanctum, as one of the two blind spots in the resistance's intelligence.
An operating-theater lair adjoining Houston's throne room, unseen by any spy or changeling.
The impenetrable command chamber of The Madness, and a hole in the crawlers' intelligence picture.