Sounds like a positioning problem if you're getting subject to a lot of attacks.

There are 3 height platforms to choose from:
- Being on the one with switches turns the fight into an artillery duel; focus-fire on Mind-controllers and crossbow Duergar, and the rest are easy.
- Central moving platform gives good arc of fire, but you're subject to attacks too. Use potions of invisibility when hurt for a couple of rounds of healing. Having the Jump spell for fast repositioning helps too.
- Ladder height platform is good because some duergar run around the long way to get you, splitting their numbers. And it has enough depth to retreat after shooting to force duergar to waste time dashing.

In tough fights like this, accuracy counts for a lot. You want consistency, not big swing gambits; pick +1 weapons over special powers.

Spellcasters need to be shut down fast. Silence them, use Darkness to break line of sight, Grease them prone where they'll lose concentration.

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Tbh, fighting the entire duergar plus Nere all at once is the toughest fight of EA. Are you pulling out all the stops? Have you optimized gear and spell selection? If you've got Speed potions unused or Revifify scrolls untouched, you need to cut loose. This is it!

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Back to Lae'zel, for half this fight she's a ranged combatant shooting Darkness arrows, throwing Void bulbs, bombs, you name it. She might start the battle with a few easy melee hits, but then it's Jump time. Once duergar are split into groups can she then reengage in melee.

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Level 5 is deceptive. Yes, character attack power has almost doubled, but no, character defence has only improved about 20% maybe less. My level 5 paladin with AC19 and hp49 got dropped by 8-10 goblins. That one extra hit did it. Got to still pay close attention to defence.