I know it isn't necessary to do the whole Beholder city but I just like to clear out every area (who am I kidding... I like kicking ass!). The only problem is that I keep getting my ass kicked. Anyone have any ideas?

ITEM SPOILERS
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Buy the shield of Balduran from Dierdrie in the adventurers mart since this reflects beholder rays back to their source. You just need to wander into beholder city and it's a breeze. You need to get the bonus merchants from the collectors edition of from Baldurdash for this item.

The cloak of mirroring found in the centre of the Shaugin city has the same effect *provided* you don't have ToB installed, otherwise it only absorbes magic damage.

Either of these items make beholders extremely easy.