Hi. I'm going through Baldur's Gate and the expansion (with the canon party) and I have a lot of trouble with Aec'Letec (the bonus boss of the expansion).

I know about magic resistance (I have a potion of Magic Blocking on my character) and that I have to kill the cultists beforehand, but the whole fight seems to be entirely relying on luck (my mage musn't get paralized, Aec'Letec better get paralized by his own spell, ect.). And for some reason, whenever I seem to be doing well, my character explode for no reason (and Aec'Letec reappered on top of him).

I've died at least 20 times on that one boss battle. It seems to be entirely reliant on pure luck. Is there anything that can be done to level the playing field (or at least make the battle winnable)?

I'm using the canon party (Imoen, Khalid, Jaheria, Minsc and Dynaheir), so maybe I'm handicapping myself too much. If you need more information, just ask.

I want to play Baldur's Gate 2, but I feel that I have to finish that one first.

Thanks in advance.

Summons. Summons is the answer to Aec'Letec. The whole purpose of them is not for them to kill him, but to keep him occupied while you deal with the acolytes. Get a wand of monster summoning, and have it recharged before the fight. The second most important point is Aec'Letec's Death Gaze: you have to keep an eye on every one of your party, and have your spellcasters memorise Dispel. It's the only way to remove Death Gaze, which will slowly kill anybody afflicted with it, eventually turning them into a ghoul/ghast who will attack the rest of your party alongside Aec'Letec.

Do not bother buffing, since he likes to dispel those, but do use rings and potions of freedom to prevent you being held. Once you've dealt with the acolytes, just keep the summons coming, and pound on him with your best ranged weapons and ammo; melee only if you must, but have plenty of healing potions.

Otiluke's Resilient Sphere also worked for me in this fight, although I think Aec'Letec has high magic resistance, so using this spell is a bit of a gamble, but if it works it gives you some time to finish off the cultists.

As Hickory said buffing really is pointless, since at least one of your characters will be affected by Death Gaze which you have to dispel, (unless you want to say bye-bye to the afflicted character) and that will debuff your characters anyway.

It's not just his magic resistance, which is 50%, but the fact that (a) he has excellent save vs. spell, and (b) a successful save vs spell completely negates Otilukes.

To the OP: he is completely immune to all non magical weapons, Poison, Fire, Electricity, mind spells and polymorph. He has 50% resistance to magic, magic cold, magic fire and cold. So your best option is Acid Arrows, since acid is his only weak spot.

It might be a good idea to have a couple potions of speed on your best warrior. That way he can get extra attacks in, and if it's dispelled, just drink another. I've found this to be useful when I fought him, anyway.

It's certainly winnable with the canon party: I did it, after some frustration. I hope you've figured out that you need to kill the cultists before killing him, otherwise he'll 'respawn' by replacing one of the remaining cultists. If you're high enough level to cast it, or have a scroll of it, there's also one (slightly cheaty) way to do it, which relies on the fact that, in the script, Aec'Letec has a lot of hp and abilities, but is considered level 1. See if you can make use of that information.

I beat him in vanilla BG1 without mods the following way:
- take a thief with bow and arrows
- place him next to the door to the demon room, use stealth, let him enter the room ( he alone) and get into a corner where you cannot see the demon before stealth wears off
-Kill all alcolythes with arrows, take care to use stealth once all alcolythes in your view are dead and you move to the next corner
-Once all alcolytes are dead all other chars can go down and beat him (with the help of summons and all other things mentioned above)
note: In BG2 all demons can see through invisibility. This might not work with mods, especially those were you use the bg2 rules. I guess my thief had the cloak of non detection, but I am not sure and I don´t know if this had any effect.

Would that spell be Color Spray, by any chance?

I guess it could work if Dynaheir doesn't get "Held" right at the beginning.

It woudn't. Remember that he has quite high magic resistance, so whatever spell you use should have multiple chances to get through that resistance before the effect ends.

I can only think that you must be speaking of a spell from the BG2 engine -- TuTu/BGT -- since the highest spells in BG1 are level 5, and none are going to finish Aec'Letec off in a timer-based fashion, which you seem to be referring to. The only level 5 spell that comes close is Cloudkill (4 +1-6 HD with saving throws vs. poison), but Aec'Letec is completely immune to poison of any kind.

I recall hearing that the demon's "turn party members into ghouls" ability counts as a gaze attack, meaning that a Potion of Mirrored Eyes will make you immune to it. I think the inn in Ulgoth's Beard has one for sale, but finding six could be troublesome.

Greater Malison -> Slow makes him much more manageable, but Dynaheir can't cast Enchantment spells, which is a downer. Still, if you dual classed Imoen to Mage (it's canon!) or if you can find some scrolls, give that a go.

Well I'm not sure if it was a potion of Mirrored eyes that did it, but personally I used every kind of potion and defensive scroll I had on my tank character (including magic blocking, mirrored eyes, defence, etc...) and he was never affected by the Death Gaze ability.
That left the rest of my characters free to slaughter the cultists, then finish off the demon.

I was using Sword Coast Stratagems though, which may have changed that ability even though it's supposed to make fights harder.

Certain conditions have to be met before Aec'Letec will use the Tanari Death Gaze, and if I remember correctly one of those conditions is that it never fires on the nearest enemy to him, though I could be wrong on that. If that was the case, then your tank would be very vulnerable to paralyse and vampiric touch, but less so to the death gaze.

I am referring to Cloudkill, which I picked up from another site, and which I used successfully: after a could of rounds of successfully resisting the effect, he went from barely injured to dead in one round. Twice, in fact, as the first time not all the cultists were dead yet.