Yes, it's the famous Epic Divine Encounter that I'm stuck on. I want to finish the game before starting a new v6 game, but it doesn't look like that's going to happen in the next month or so with the tactics I'm currently using.
OK, so here's my party:
Vagrant protagonist - 32
Minsc (Berserker) - 36
F/M - 23/20
Anomen - 38
Imoen - 30
Nalia - 30
I've forged every IA item that I want, I've got JD and FoDaW on my Vagrant, both halberds and Staff of the Ram on Minsc, Hammer of Thor and Death of a Thousand Cuts on F/M. I've got Gaxx +5 but all other rings/cloaks are of +2 enchantment, in harmony with the next version. I'm not using rod of resurrection, also in harmony with v6.
I summon basically everything I can, 5 swanmays, 4 mordy swords, planetar, greater djinni and a noble spider. Most of the summons go straight for the prince to delay him while the greater swanmays and the queen help my warriors. I focus the Supreme Golem and have both bleeding weapons equipped in main hand. I usually get him down to badly injured before the first wave of the rakshasas spawn and then the bleeding effect may or may not take him down to near death while I focus the rakshasas. I normally kill the first wave of rakshasas before they can do any harm and then finish of the SG quiet easily. Then I focus the Ultra Golem (with crushing weapons equipped in main hand) and by the time the first UG is dead my summons are as well (if not earlier).
Next, I focus the Elemental Golem or the second UG, whichever is closer. I try to station my F/M so that the prince is more likely to attack her. I've never managed to get farther than this; the newly spawned rakshasas I can't kill fast enough either because my HLAs are exhausted or I can't reach them because of all the minor golems that block my every move. And then comes the dreaded "purge magic" something and my F/M is chunked (!) within seconds either by golems or >9000 ADHW. When the F/M is gone the prince is free to attack my vagrant or Minsc and my resistances are no more resistances. And then my party is history.
I've got 5 Barbarian Essence potions; Minsc drinks 3 of them while my vagrant only drinks 1 which is enough to get both up to 100% physical res. with Hardiness. The last one I'm saving for later use in the battle, in case the duration expires. I'm using the dual halberds tactic although I favor Poseidon's. Nalia's job is to summon more help, mainly MS, and Imoen's is to cast Wish and Remove Magic. Anomen is obviously a sitting duck, casting GR and occasionally refreshing Regeneration on Minsc, if he's able to get out of the wall-of-golems that is. I try to keep the warrior's HLAs up all the time.
My F/M has got 51 PFMW scrolls but I haven't been able to use but 1 of those (I normally use memorized spells because they are faster thanks to the Amulet of Power, even though I know scrolls can't be interrupted, with careful timing I've never been interrupted). I buff my F/M so that it takes 6 RRoR to take down her SI:Abj. Or one purge magic
I'm playing on core rules. Shouldn't this be an optional battle?