"second floor down from the top (same floor as NPCs Sherri and Jaris)."
FYI: The floor with Sherri and Jaris is the 3rd floor down from the top. If you use your height filter on your map, you will see Sherri and Jaris noted.
Note: For all map points of nameds in Fear Itself (for "thuledream.txt" map files), see this quest entry.
Undaleen spawns on the second floor down from the top (same floor as NPCs Sherri and Jaris). Multiple PHs on this floor including the roamer near 765, 370, 115 (at a dead end). It hits for a max ~11,500.