OK, I give up with the hive mother & her allies. I've been stuck on this battle for nearly 3 weeks and at least 40 reloads. The best I've ever done is get one of them to 'badly injured'.
I have a reasonable party [around level 20]. What hurts them? Most of my weapons are ineffective, summoned monsters last about 30 seconds and offensive spells have no effect at all, even after Greater Malison/Breach/Pierce Magic etc.

I am having the exact same problem. Not even lower resistance has an effect! He is even time-stop immune, that is he walks around and attacks during my time stops! PLEASE HELP!!!

Time stop is a death sentence against Demogorgon, for everyone except the mage casting it. [img]smile.gif[/img] Improved alacrity is the way to go. With the Robe of Vecna you can blast down his defenses in no time and let your whirlwinding fighters hack him to small chunks. Ideally the one he's attacking is immune to disease and has massive physical restistance, but he doesn't have _that_ many hp so with two or more warrior classes on his case he'll drop pretty quickly.
As for the preceeding battle - I've not done it at as low a level as 20, so I don't know how hard it'd be. I'd probably better go try it before saying anything. I'll see how my solo mage/thief gets on with it, when I get that far.

well i have the answer to your questions there "yoshimo" if you play the keep on soa before the first encounter with irenicus. do as many stupid side quests as possible become high enough level thief that he can lay done 3or 4 spike traps in the general area where they appear combined with a couple regular traps as needed you get 7 traps at most so... have all your characters hide in the northeast room and hide afterwards. my main char was a maxed out paladin with all the great trimmings. set off the portal and run. before you know it when you look back the only char, left are the hive mother which almost always is at "badly injured" the yan ti guy who shows "injured" and the last mage guy who usually says "barely injured" my paladin by means of importing over 5 games has a natural resistance to magic of 85% so the mage was not a big problem for me i left him alone. the queen is who i went for first couple good hits with the casomyr dealing 25-30 points each hit took her out quick. then kick it up a notch and hit the yan ti guy with greater whirlwind attack usually dies before the attack is over the the mage is a cakewalk afterwards.
my paladin runs on the red dragon armor, cloak of mirrors, casomyr, ring of gaxx, the amulet that gives 5%mr, the pale green ioun stone, boots of speed, girdle of bluntness(for all those great blunt attacks). its an undead hunter kit so vamps are nothing against me. i could go solo with my palidan but i like my theif and traps abilities.
for amn i run my pali with yoshimo and korgan (edwin if im bored) but i keep the party members at a minimum so that my main char build exp. quicker. and if you think that group of guys are hard to beat the demigorgon is even worse. i cant beat him without laying massive traps before i attack him.

Made it!!

The monsters move at different speeds. Hide in the east room. Summon a few monsters to keep the enemy busy when you open the door, haste everyone, then open the door and make a run for the south room. The fastest enemy [can't remember which one] gets there first and you can shut the door behind it then chop it to bits. This can be repeated back to the east room, then back south again - 1 enemy at a time!!

Aw, that has to be my most favourite tactic - when fighting lots of things, run away to a convenient door, a nd coax one through, then shut the door. I used to do that in nalia's keep with umber hulks, otherwise they whupped me. I'm so glad someone else does this *grin*

another fun way to kill demogorgon really really cheesy,

highest lvl mage cast timestop shapechange (mindflayer) attack timestop over demogorgon dead.
kinda sad really but another effective cheese move.also good on chromatic demon.

robo i know where you are at,,,
first room inside planar sphere