Wow, this thread's been busy since I last caught up!
Here's my point of view. I generally agree with Echohawk about mostly sticking to the original monsters, but I do agree that the precedent in converting this type of critter is to boost them. So I agree with making them a lower-level epic threat (CR 20 to a max of 22). So the problem I have with the proposed abilities is that they'd push him well above that CR range. We should really be aiming for the avatar of a low-level demon lord or similar fiend (ie, better than the silly little aspects but not a divine-level threat). I don't necessarily have a big problem with putting the overpowered stuff in an underbar, but I really don't find them reasonable at all for the base version.
I don't mind cutting the two SQs you find objectionable from the base creature.
Is everyone OK if we move them to an "optional underbar" in the the
Ythog-Nthlei Working Draft?
Nookie would prefer more variability in the methods of destruction in Beyond Death, so we could leave that to the DM's option too, with the "divine ranks" as an example.
e.g.:
Beyond Death (Ex): Ythog-Nthlei can not be killed. If brought to -10 hit points his body melts away, leaving nothing but an unspeakable stain, but he will reappear at some later time or on some other plane without suffering any penalties for having died. He reappears even if the his body and spirit are annihilated. The time-delay and distance of Ythog-Nthlei's reappearance after death is at the DM's discretion, but may be considerable (e.g. 1d100 years later on the spot he died, or immediately on the lowermost layer of the Abyss).
Any effect that permanently incapacitates Ythog-Nthlei or renders him helpless for more than a month (petrification, being ability drained to Wisdom 0 or Dexterity 0, long-term paralysis, polymorphing into a non-combative form, et cetera) is considered to have "killed" him and triggers his rebirth. Note that sleep effects do not trigger Beyond Death.
It may be possible to circumvent Beyond Death and permanently destroy Ythog-Nthlei, but what the means to do this have been left to the DM. The method is likely to be a deep secret requiring intense research or a hard quest. Suggested examples are: Ythog-Nthlei will stay dead for good if he is killed by a creature with divine ranks, a blow from a lawful evil titan wielding the Dark King's
blacklight mace, poison from a creature with both the pseudonatural and paragon template, or an epic spell that does more than 555 hit points of damage.
