For information about this project, you really should consult the official "'Demon's Due' Defined" Journal. [link]
I've had this design floating around since the beginning of Bare Necessities when Elina was going over her diagrams of the catacombs and such beneath Dernhem. I figure it's time to let folks see it for a number of reasons, the first being that the next few pages of Drea's encounter with the "tall figure" in Coils of Fate are going to range all over the Undercellar, and I think it'll be cool for people to reference where they are relative to where other things have happened.
And, just so we're clear on a few key facts implied on the key above...
A. Valerin was gagged by Albert on these stairs.
D. As of CoF 43, Elina is locked in the second cage from the left (the same one Valerin occupied), Deirdre slaughtered the horde of gremlins and jackrats in the three sections of this room (above and left), and Deirdre's fight with Callista started in the left portion and ended in this portion in front of Valerin's cage.
E. Callista found Albert's dying body right inside this room.
F. As of CoF 43, Callista is tied in a strappado in the lower-right portion of the room, and Deirdre and Avora occupied the two central tables at the beginning of Vision Impaired.
H. The Cat-shade was defeated here.
I. Callista was defeated by the Witchwax here.
M. The left room contains the corpses, while the right room contains the "trophies" and mementos of former victims, while Annalae was defeated by the net of cocooning cord against the right-most wall.
N. This room is directly beneath the large common room of the Fair Harvest Inn.
O. The phantom images of Valerin, Avora, Deirdre, and Zirena are here, along with other Fadings that we haven't seen.
P. Jervil's bed is against the far right wall.
R. The tall figure addressing Drea on CoF 44-48 comes through the upper-left entrance.
S. It's hard to see where this is in the top, center.
There are a few goofs and inconsistencies with some of the images, but not many.
A close-up of the right-hand side with the heroines' paths colored in can be found here: [link]