Save or Die: There were SoD effects in 3e
Thank you. It'd be awesome if you'd stop saying there weren't, going forward.
If what you mean is "at low level, 1e fighters had crap saving throws,
and at the highest levels had the best saving throws in the game and could expect enough bonuses from randomly generated magic items to fail only on a natural 1, even before name level, PCs casually drinking poison for the flavor because it was essentially harmless was a running gag," just say that.
However, fort saves were easier to make in 3e compared to AD&D at the typical levels PCs faced them. In 3e, you added your Con modifier to your fort save, and level progression bonuses outstripped the roll needed in AD&D.
Yes, you added your CON bonus, no the progression did not outstrip the 1e save matrix, because DCs rose continually through your career, while save penalties even at high level, were very rare in 1e. A 3e 'good' save was lucky to tread water, if the DCs you faced were being optimized even that would fall behind. Bad saves - the other two besides Fort if you were a Fighter - fell behind /rapidly/.
In regards to poisons, in 3e you got ability damage.
Ability damage was pretty awful, actually, it's not like your abilities went up the way hps did, so it was damage that bypassed your most significant margin for survival, and, it ability was important to what your character did, it was also a death-spiral effect - and if it wasn't, if it was a neglected or dump stat, then you didn't have very far to go before you were killed or rendered helpless by it.
In 3e, you could also choose feats to improve your saving throws. Didn't have that in AD&D.
Correct, unlike 3e, you didn't have to give up other abilities to desperately try to keep up one of your three saves against constantly-rising save DCs, in AD&D they all got better across the board just by leveling.
Level Drain: In 3e, you don't lose nearly as much, and you regain those levels after 24 hours
You might recover from a negative level. Or it might become a permanent level loss. And, critters bestowing negative levels in 3e were a /lot/ more likely to actually get to do so: they were harder to turn, much tougher, and hit much more easily - often with incorporeal touch attacks.
And I'm not even comparing how 3e PCs are exceptionally more powerful than AD&D (especially casters and rogues) or how you didn't die at 0 hp.
You died at -10 in 3e, just like the commonplace Death's Door variant in the 1e DMG. And, as much as 3e PC got bigger numbers, monsters, which had stats, including extremely high STR scores for larger monsters, and feats, /and full benefits from them/ more than matched them. Monsters in 1e were made of glass by comparison.
I'm not saying 3e isn't deadly or lethal, but looking at like for like comparisons, it's not as deadly as AD&D, but more deadly than 4e or 5e. Lethality is much more than just HP soaking and damage.
Though hps and soaking damage won't get you far in 3e. A same CR monster like a Giant could demolish a reasonably tough fighter in a round, maybe two - if the fighter was optimized, it was prettymuch even money which do the huge pile of hps to the other first - and if there was an optimized SoD going off, whether from a Tier 1 PC or a Lich or something, then it was straight-up rocket tag.
3e was not so much deadly as broken, but it was still quite, quite deadly, when it broke the right (wrong) way. It was up to DMs and players to either show restraint, or optimize to a comparable degree, to make it work.
I also think it might help to distinguish overall lethality from lethality at a given level. At 1st level, lethality decreased pretty smoothly from the original game, through the TSR era, to 3e & 4e, reversing only some with 5e. But, if you look at more of the game, you find that in earlier TSR eds, the game got a lot less deadly as you got some hps under your belt, some magic items, your cleric got more protective/restorative spell options, and as your saves slowly got better, while monsters never got a whole lot harder to hit or harder to kill (though they sure got weirder and weirder special abilities and gotchyas - and the stereotypical Killer DM never lacked for ways to end your desperately-paranoid favorite high-level character), while, in 2e, monsters got quite the upgrade, becoming a much more serious threat at all levels, because they could stand up to you long enough to do their thing. That /also/ started a trend that continued, this time, straight through 5e. So, while WotC era D&Ds became less deadly at low level, in general, they were also more challenging at high level, without resorting to gotchyas and DM fiat.
FWIW. (which, if you're going for old-school feel, is exactly nothing)
