Lilah, neutral evil half-elven mage/thief, final update
I am always afraid of Durlag's Tower and the Ulgoth's Beard Cultists in a no-reload game, and for good reason. Several instant death scenarios do make playing down there quite exciting.
Lilah first cleared the upper areas of the tower, killing the ghost and tricking Riggilo. Downstairs, I carefully explored the first level of the dungeon, using Montaron with potions of perception for traps in case of a mistake (since there are instant death traps down there, I don't like to risk my main character). Since I had a lot of strength potions at this point, I always had Kagain use one. Eventually, all the tasks were finished, and the guardians to the next level defeated. Lilah returned to the surface to sell some stuff and rest before returning.
Down at the second level, I made a mistake with a lightning trap that was somehow not detected even though I stood there for at least 5-7 seconds (maybe it was just a bug), though thankfully Kagain triggered it, and he has 95 hp. Higher doppelgangers were carefully destroyed with magical arrows and Kagain tanking. Near the end, Viconia summoned some skeletons, the party used some buffs and the dwarven doom guards were attacked and quickly dealt with.
The next level started easy enough, with the greater wyverns posing no threat and the skeleton archers killed by Shar-Teel, using a protection from undead scroll. However, after clearing the third path and completing some of the elemental rooms, I entered the ice room with a low hp Kagain (I was out of healing spell since I didn't rest between the beginning of level 2 and here, and I didn't want to waste any more healing potions since I was using a lot of them just to save time), and he got held and killed right away despite his great saves (should remember using a potion of freedom here - also, I didn't have boots of the high north thanks to low charisma in this run, and didn't bother to keep scrolls or potions with protection from cold - they might have saved Kagain here). The party managed to shoot the remaining frost creatures with multiple fireballs.
Lilah returned to Nashkell to raise Kagain. On the way back, disaster struck - ironically, Kagains death would not be the dwarfs downfall, but Montaron's instead. While reentering level 3, the halfling got too close to the constant fireballs, and one hit was enough to chunk him. Down to 5.
Now, time for the chessboard. Everyone drank a potion of absorption to protect from any lightning bolts. The battle was tough. I underestimated the opponents speed. The party started off fireballing everything, though some party members were wounded, and I had to focusfire specific enemies using lots of magic missle spells to keep the group alive. Eventually, Kagain managed to surround himself with the remaining foes, and eventually, the King died.
As for the last level, most parts were relatively easy. Kagains ac and saves protected him from all opponents, and I had potions of freedom just in case. Summons triggered the instant death traps. The demon knight, however, was another story: I made the mistake of having Shar-Teel join Kagain in melee combat instead of letting her use her bow, so they both got their buffs dispelled. Despite her fire resistance, the following fireball chunked the fighter - she was avenged quickly, but - Down to 4. The tower takes its toll.
I was extra careful when reentering the Beard: Lilah, Edwin and Viconia all drank invisibility potions as soon as possible, so Kagain was the only remaining opponent for the cult assassins, giving the mages the opportunity to unleash their powerful combination of greater malison and emotion, taking out the 3 of the cultists.
After resting and buffing (including with a lot of potions and the invisibility spell), the tactic was reused for the next group, with much success. The enemies inside the building were smarter - the assassins didn't attack Kagain, waiting for Edwin to reveal himself - but his mirror images protected the mage, and with the help of some magic, the party was victorious again.
Time for one last rest, and buffing with everything left, including mirrored eyes and magic shielding for everyone. Edwin also had 3 death cloud spells prepared. The spell was used to kill Aec as soon as he reappeared each time, while the party sped up the proccess by killing the cultists one by one. Eventually, none were left, and the demon simply died.
Lilah finished the run as a level 8/8 mage/thief. Oh, and in Baldur's Gate, I spent some gold to increase her reputation to 18 before reporting to Belt since I plan to play with a good party in BG2 - turns out my reputation is 20 in Amn anyway. Why? Does BGT set it to 20 automatically?
Anyway, see you in BG2!
Enuhal