Actually, my mistake, I was using the N! number there, the earliest a nightmare arachnotron cave should appear (assuming I have the difficulty numbers right) is 46 on UV. On N! they can start at 43. Assuming the wiki is accurate, this difference isn't that big. The real problem is that you have to be able to murder your way through a pile of nightmare arachnotrons by dungeon level 43 or so, and it's not immediately clear to me what the best way to do that is.
Ah, thanks for the clarification. Yeah, without a lucky invulnerability globe on the previous floor, these would be incredibly dangerous, and I'm also not sure how I'd approach one.
Is there no way to avoid or limit the damage from them? Shamblers and cyberdemons are huge HP sponges, but their burst damage potential is weaker than many normal enemies. Is it the accumulation of damage or the burst that's the problem? Why is fire immunity mandatory, as opposed to very high fire resistance being sufficient?
It's been a long time since I've played much, so maybe my memory is not quite perfectly accurate, but I recall shamblers as being very accurate and doing very high damage. Cyberdemons come in Complexes, not Caves, and they'll soon start to annihilate all the walls near you, exposing you to fire from more and more of them simultaneously and severely limiting your positioning options. It's not so much accumulation or burst as it is aggregation - once you have 5 or 6 of them firing at you every action, it's pretty easy to get one-shot, even if you could otherwise mitigate damage from a smaller number. And 5 or 6 is a low estimate of what you might be facing even on spawn, much less later on as they start to collapse on you. Fire Immunity is necessary for Cyberdemons because as I mentioned, they tear up the walls and you're soon under attack from absolutely stupid numbers of them every turn, while lava elementals, if memory serves, have a napalm effect, which will eventually leave you with nowhere on the level to stand that isn't fire.
A nanoshrapnel shotgun would be the best non-melee option, but any nanomanufacture high damage weapon would probably be sufficient with an appropriate build. I don't think melee is required.
You are correct, nanoshrapnel is excellent for agony/pain elementals and lost souls, while other nanomachic weapons would certainly help. Of course, this does mean that, in addition to everywhere else on the run where luck is going to be key, you'll need to find a nano pack before your first agony cave. Not impossible, certainly, but by no means a given.
FWIW I encountered two late-game Nightmare Demon caves this game and cleared both of them without any significant trouble. Having the Jackhammer helped, but I suspect any build with sufficient shotgun firepower could manage.
Jackhammer was actually probably a lot more clutch there than you think - most other shotguns don't have the same potential for AoE knockback even in a single firing, and nothing else offers multiple bursts prior to a reload. A nanoshrapnel shotgun would be helpful here, but offers far less damage per shot(meaning both less killing potential and less knockback), putting you in severe danger of being surrounded and overwhelmed. However, you make a valid point - with proper positioning and a reasonably powerful shotgun build, they might not be run-ending.
Gambler's ruin is definitely the problem I would absolutely be worried about, though I think horrible normal levels should also be on the list. (Elite formers feature prominently in my nightmares.)
Yeah, I have a feeling this would be the true death of any attempt at such a mortem. Even with excellent luck for hundreds of levels, most attempts will eventually encounter a situation that can't be survived while maintaining the 100% killcount. I can't imagine many people would have the persistence to keep at this one long enough to complete it, especially considering the very high difficulty of even getting such a run started, and the overwhelming tedium and time investment required by the full N! clears.
I wouldn't go quite that far, I think the Speedrun Angelic is outright impossible ;). This one is merely almost impossible.
Actually, I suspect Speedrun is quite doable. I've never been much of a speedrunner at any game, and I managed an
8:07 N! win on graphical mode after a relatively small number of attempts. Granted, that's still less than half the speed demanded by the badge, but I think that if someone were to dedicate enough time and practice to speedruns, they'd eventually get a set of floors that was winnable in that time. A big part of that is building up the instinct needed to react almost instantly to various situations, and then have that instinct be correct during the winnable run. In any case, while the number of attempts to achieve this would certainly be higher than for Centurial Archangelic, the time cost per failed attempt is, by definition, almost insignificant.
Now, if we want to create a Speedrun Challenge worthy of an Archangelic Badge, might I suggest Compet-n Silver Cross on N! Ao100? ;)
Of course, if we insist on Archangelic Badges requiring Archangel challenge games, then Compet-n Silver is probably out of the running - maybe N! AAo666 in under three hours?
Either one is about 3-4 floors a minute(18 seconds per floor for Ao100, or 16 seconds per floor for AAo666), which is slightly more lenient than the current Speedrunner Angelic - the extra challenge comes from the lack of exploitable special floors, and the marathon grind(note that the slowest actual award, Compet-n Silver, would require a pace of 22.2 floors per minute, or about 2.7 seconds per floor[!], which I suspect is well and truly outside of the realm of possibility - probably even for an optimal AI, at least in a number of attempts that could be made in anything approaching a human lifespan).