Aec'Letec... (strategy spoilers?)
 

Hehe, took him out without losing a single party member, infact the only one who took any damage was my PC.

Party: Myself(Paladin), Minsc, Khalid, Jaheira, Imoen, Dynaheir

So Everyone is hasted, blessed, defensive harmonied. Me, Minsc, Khalid, Jaheira all down Potions of heroism, everyone gets a potion of mirror eyes. We enter the room and I have dynaheir fire off a couple cloudkills in either half of the room. Meanwhile Imoen is firing arrows of detonation at the middle cultists on either side. At the same time Minsc, Khalid, Jaheira and I take out the two nearest cultists.

Before Aec' even gets a chance to move the room is clear.

Caution: results may vary, the above result occurred on something like my 3rd or 4th try. The other times 1) Imoen wasn't using detonation arrows, 2) I just had lousy luck with to hit rolls. and I'd lose at least half my team just because Aec hits HARD.

Re: Aec'Letec... (strategy spoilers?)
 

That will really do the trick.

Re: Aec'Letec... (strategy spoilers?)
 

Well, I'd read that Aec' was incredibly weak to the spell so I decided to give it a go. It seemed to have little effect on the cultists but definately did a number on Aec'. the detonation arrows are like rapid-fire fireball spells (if by some odd chance anyone didn't know). And they pretty much did the trick on the cultists.