Okay I have nearly finished the game now. I'm in Murok, which I presume is the end.
The demon lands were a breeze after beating the Necromancer. I defeated Bhaal losing about one quarter of my stacks, then did all the demon quests and closed the portal. The only issue I have in my game is money. I was getting quite worried during the labyrinth because I was down to under 200,000 k at one stage, with no end in sight. I find that I am spamming Phantom pretty much every turn, and using the Drain Soul rage spell (kills 40% of stack with 35 rage, with only 1 turn rest
) I'm sure there are better ways of doing this but it is working just well enough to win the game on Hard. I'm sure Impossible is another matter though - I've no idea how you Russian guys were able to win like this.
I think the Ragebox is capped at level 30? The red demon seems to have stalled there. Interestingly, my electricity demon is still on level 16 or something. I don't have much of a use for her at all (Gizmo is good, but too weak in the end game).