Contains Spoilers
[QUOTE=Sytze]Three curious questions (mheh, else I wouldn't be asking them, non?

)
1) How many level 9 spells did you have in the final fight?
2) What were you basic HLA's and mage spells set-up?
3) Where did you get your strength drained?[/QUOTE]
1) Three: Planetar, Spellstrike, BBoD
Not knowing that there is more than one round in the fight, I used all three in the first round (I wouldn't have made it without the Planetar anyway and used BBoD for the dragon and the Orb).
2) 10 GWW, 2 Hardiness, 4 Spike Traps and 2 Time Traps set up losely in the area (the Time Traps helped a lot). I have practically all other available F/M/T HLA at least once. My memorized spells included an array of abjurations, buffing and some damage stuff, the usual. Pre-Buffing consisted of Stoneskin, Prot from Fear and Evil, Fireshield B/R, Spell Immunity Abjuration, Minor Globe, Imp Haste and whatever I got from several items. I also had a Chain Contingency loaded with three Abu Dhazims set to target my last attacker at 50% HP, which went off in the first round. The pre-fight summons consisted of the Planetar, three elementals (earth, fire, air from the item mod elemental staff) and a Simulacrum.
3) Second round. Jonny entered the arena in Slayer form with an of army shadows. I was "naked" - all my things were lying in the middle of the room and I was near one of the stairs to the test areas. I sunfired some shadows and ran to my equipment, but the remaining shadows and Jonny managed to surround me completely. I got drained to Str 3 before I could say "damn". After reaching the equipment, I picked up my rings, cloak, strength girdle (brought me up to 5) and Helm of Brillance and sunrayed the shadows. I fired a trigger with Stoneskin and Fireshield B/R. Used a potion of Cloud Giant Strength, but it didn't help much. Next I got a Simmie from the Helm of Vhailor and further managed to survive my "weak period" with the help of item based summons and some spells. It is truly annoying if you can't move - but moving would also have me taken away from my equipment, which I couldn't carry or equip (weapons or armor) and picked up / used only one item at a time for that reason.
As for my surrender in the third round - I guess I can get through all fights with a different setup and a little luck (one Planetar each round should help). But Jonnys cyclic casting of all the high level stuff got on my nerves, because this was not a fair fight anymore. I had to waste my remaining Time Stop and Death Spell scrolls on armies of Mordekainen Swords, just to see him cast Time Stop + Imp Mantle + Imp Invisibility + Stoneskin + Immunity Abjuration + an array of other buffs and summons every fourth round, while I was already low on fuel from the first two battles. Maybe this is easier with a party, because a single character has too much work to keep the summons at bay while Jonny keeps his personal defence up. He simply wore me down and I was too annoyed to come up with something creative.
Anyway, I have a save of the end fight and may try this later again. It was by far my most difficult BG2 fight ever, made Imp Twisted Rune look like a walk in the park (for comparison, I did Imp Twisted Rune twice without any significant problems or reloads with this character).
The Imp Kangaxx guardians on the other hand gave me a perfect fight. This fight alone is worth to play through the whole game and the real fun was to take it outside, because the fight took place over a big area with different things happening in different places at the same time. First, I lured the skelly warriors up the stairs in the docks and killed them out of range of innocent bystanders. A Simmie kept the Liches busy. I ran back past the liches to the corner near the light house and into five Hakeahars that drained some of my spells. In the mean time, one lich started to gate in a Pit Fiend, while I had a bunch of Mordekainens sent into that area. Add the Telly Field cast by one Lich, my elemental summons that came on and imagine the chaos that ensued outside Mae'Vars place. Totally insane.
@Fable - sorry, this was supposed to be in the SoA forum, could you move it there?