I've just duffed up the guardians of the final seal (Y'tosser, Hive Mother, et al) at about the sixth attempt and wondered what tactics people used to defeat this very tough group.
Boo won't let me use cheese like traps and, if possible, "oh dear, I should've rested" after having entered the fray. My party was Avenger (self), Minsc, Sarevok, Jan, Aerie and Anomen. Previous battles had used up all my summonses, though I had plenty of Remove Fear, Death Ward and Chaotic Commands.
I had to lure them off into the side rooms, which has a whiff of cheese about it, so I wondered what others had done, apart from setting hundreds of traps and summoning half of Nato.
Oh, forgot to say, the best bit was that it ended with Jan nailing the blade barrier dude with a crossbow in the kneecaps.