Did we miss anything in this location? Is there something we didn't discover? Let us know!
1 - DRIDER CHIEF
The castle is crawling with driders, drow/spider hybrids. The best way to deal with the first party that you run into is to take out their chief, then the magic users. The regular drider are easily dispatched after that. Why is the chief so tough? He's got a shortbow that has unlimited arrows, which deal lightning damage. Well, if his constitution had been higher, it would still be his. Now it's yours.
2 - ASSASSIN DRIDER
The assassin drider in this room is worth noting, I guess, since he's more powerful than the drider chief you just beat. Why didn't he join in the fight next door? Whatever the reason, you now have his +8 dagger which you can use, if you are an assassin, or give to Nathyrra.
3 - THE FOOL
Castle Throne Room
I buffed up, expecting a fierce fight in the throne room, but there's only a fool sitting on the throne. He tells you why you've been picking up mirror pieces all over the city. The mirror was powerfully magical and allowed the queen to spy on her people. When she used it to spy on Halaster, he pulled the entire city through the mirror into the Underdark then broke the mirror. You need to get all five shards, but Sabal has one of them, so once you've gotten the other four, you'll have come back here and fight her to the death to get it. You can also loot a belt of fire giant strength, a ring of major electrical resistance, and her flail. Once you get all five shards, the fool will repair the mirror thus restoring himself and the queen to their proper forms. Before the city disappears, the queen will thank you and let you keep the mirror, which casts a bunch of spells that dispel invisibility.