Ok, after some tedious work, I found out the culprit, though the results are somewhat unexpected... it was Supreme Magicka, as soon as I deactivated it, the ctds went away. I dont really know why it happens, and I dont know why noone else here is having that same problem (since both are mods for mages mostly, after all), but I cant find any solution to it... any ideas?
Here's the quote for that mode from the .ini file:
turns off the central spell script- everything related to enemies (spell effects,;Poison Damage, etc). Adds the token for the spell knockbacks and staggers
So I suspect that SM does something to the spellcasters here - i.e. the liches and ghosts - that the game doesn't like. The most complicated aspect is the handling of summoning spells. I'd look there for suspects. Perhaps it would be interesting to know in which way the liches here are different from the standard ones.
@indefiance:
Just let me know if it gets too ridiculously hard,,,I want it difficult, very difficult, but not impossiblie.
I've made it through the Avalon quest. Phew....what a voyage. Truly epic, as is its reward and the whole architecture down there. No "impossible" enemies here except the one that's supposed to be, I'm glad to say. The liches (those in the Deepness as well as elsewhere) are the worst by far, probably because they've been boosted by Supreme Magicka. The wraith is difficult mainly because the traps in the Deepness distract you. The other Avalon enemies, even the higher-level ones, were fairly easy for my sneaky mage, but if I hadn't almost always noticed them first things might have been a bit tricky at times. As it was, the only difficult ones were the group of 4 at the center of Avalon. And, of course, the overlord which I couldn't kill at level 16...but I got his ring.
I guess things might be somewhat more difficult for non-mages or non-sneaking characters.
So, enemies are OK but I think you overdid it a bit with the long walks - especially in Firaga Dorn. And that insane stairway! I jumped down once, just to see how long the fall would take. It was a long way down

I also noticed the amount of loot down there is staggering... I don't know why these enemies are carrying better loot than those in the rest of the game at this time, but I got *lots* of absolutely high-class magical equipment, even if I don't count weapons and armor I normally wouldn't be able to carry.
Two questions:
(1) To get into the mana well, you have to activate the door frame, not the door. Is that as intended?
(2) I'd gotten a soulstone from the grave. A little later it had vanished. What was it for?