Session Six
Chapter 3. Betrayers' Rise level 1
The driders where a vicious fight, and the stained-glass window puzzle was vicious too, when one of the PCs failed their dance check (note that they assumed a different character had to dance each time, but this isn't actually specified. The alternative clue was basically impossible to find, since no one had see invisibility. So it was trial and error, and a shed-load of psychic damage. I think they would have been better taking the smashy smashy option! Fortunately, they did a lot better with the supplicants' pit, since the bard had calm emotions.
Generally, I think this dungeon relies too much on you must know this spell to proceed. The party lost other options due to not knowing Abyssal or Comprehend Languages. It feels almost Tomb of Horrors-ish.