Sword of Chaos is a 2-handed weapon. I would therefore take Adjatha and use a shield. I am very fond of shields.
Importing a character from BGI would not necessarily have saved you from the stuff in the sewers. You have taken on a couple of the more difficult quests in the game.
SPOILERS
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There is a shield for sale (assuming you have the bonus merchants) in the Adventurer's Mart which can help you take out the beholders in the sewer. There is also a large number of undead. If Aerie is your only cleric, you might want to switch out for Anomen (in the Copper Coronet). He is a better cleric and might be able to help you with the undead. As for the Planar Prison and the bard--if possible, leave it for later!
It's tough. If you're stuck there without a save, well, use your wands, potions, and scrolls. And buff a lot. Cloudkill from inside the fog-of-war whenever you can.
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END SPOILERS
Sillara