The actual NWN difficulty slider setting for PotM is "D&D Hardcore".
The HARDEST difficulty that NWN allows is actually called "Very Difficult", and has all the same rules as D&D Hardcore except all NPCs do 200% damage, which is not the case here.
Just to clear up any confusion that the replies might have given, here is a quote of what exactly our rule set entails:
Single player: Full PvP (Fireballs and other area effect spells will hurt party members.)
Multiplayer: As per server setting. ((POTM is Full PvP, and the above rules listed for Single Player will apply))
Critical hits on PCs.
Attacks of opportunity on players using ranged weapons.
Attacks of opportunity on players using potions.
PC damages normally.
NPC damages normally.
Players can die.
Sleep spell on players functions normally.
Domination and charm effects on players cause daze. <----- ((This one sometimes slips by even veteran players. It's a good thing to know.))
Hold, paralyze and stun effects on players function normally.
Confusion effects on players function normally.
Fear effects on players function normally.
Petrification is permanent.