The red lines in the hallway leading up to here are heavy, barred iron doors with locked gates, much like the ones to the cells in room 1. A DC 15 Thievery check will pick the locks.
The chamber itself contains six 10'X10' cells with heavy metal doors of solid steel. Each of them have a narrow slit at about eye-height, with a sliding panel over it. Each door has a numeral 1-6 scratched into it. If the doors are locked, it is a DC 20 Thievery check to pick them. The door to cell 5, in the south-east corner, should be locked; it contains a rough-hewn tunnel to room 5, hidden under a trap door under dirt (DC 15 Perception, DC 17 Thievery, +2 to thievery, or potentially Arcana (DC 20, you're following the malevolent feel from the cells) checks to disarm with previous successful perception rolls).
When in this chamber, an Arcana 20+ check detects a faint malevolent energy from each of the locked cells. If actually in one of the cells, the DC on that check drops to 12 for the cell one occupies. A better check under those circumstances (17+) implies that the energy is necrotic, and growing in strength.
Each cell has 1-3 silent skeletons collapsed upon the floor, or on small, wooden stools, or the like, and one Skeleton slumped against the wall on the outside of the cell. If the trap-door is triggered without being disarmed, they'll wake up and attack. I'm going with nine Tortured Skeletons, plus a Stonespawn Skeleton in its own cell, and two Skeletal Legionaries. Between them, they should drop around 2o sp total in corroded coins. One of the legionaries should be the one that was outside of the cell; this one has a large, iron key hanging from its rotted belt.
A room that looks like it was used mostly for hiding out than a potential escape route. There is a dusty cot piled up with rat-nibbled blankets and pillows, oily rags, a lantern, a deck of old playing cards, and numerous other oddiments and living detritus. A stack of books are piled up in one corner with many pages torn out; largely, they look like lists of names with various numbers beside them. A streetwise check (DC 15) or history check (DC 17) reveals that it is a book of prisoner names. Potentially, one of these is Palambro Alieri.
One of the corners contains what seems to be a crude set-up of alchemical components from what looks like prison cookware and cutlery. There's perhaps 50 gp worth of Residuum there, and a vial of crimson aether. There is also a page that is another list of names and numbers on one side, and on the other, says the following:
"These are the ways of travel, for the lost:
--By Fiery Air
--By Direct Command
--By Forgetting what is True."
So I'll be doing room 3 in a separate post, sometime when I have the brains to do it.