I was playing with how to handle super-strength in a system design I've had going for a while, and started thinking about one of the limits I wanted to impose on the system: I wanted to keep the mechanics from being able to create damage values so high that even the most grazing hit (this system incorporates degree of success into damage calculation) nonetheless amounted to a fatal blow in one shot.
My inclination is always don't get cute, don't get clever. You want to do that, just do it. Maybe the most a grazing hit can ever do is 50% of the target's health. Or 90%. Or whatever you find easy to calculate.
From this I realized what the real goal of that limit was: I have always been profoundly resistant to situations where a single failed roll, or even a single player choice made in ignorance of the circumstances, can cause character death. Hence, the title of the thread: the One-Roll InstaKill -- this encompasses more than combat, of course, and includes things like saving throws or even the classic sphere-of-annihilation-in-the-statue-mouth trap.
This requires clarification as to what "single" means. I don't think I've ever experienced starting up a new session then right off the bat everyone has to roll save or die. Or for the first time the GM asks, "What do you do?" and the answer leads to instant death. That said, it's not always going to be obvious what "single" means since any instance is only ever arrived at through a series of dice rolls and decisions. It's clear in combat when you say "no single hit", but other than that, what do you mean?
What about Save-or-Die poisons in old school D&D? Generally the monster must first hit, then you fail a save. That's two rolls. Although there's no decision-making in between. And so in a way that amounts to one less-likely-roll. Well, what if you're fighting a bunch of goblins? After your turn, 5 of them attack you, and out of some freak chance they all critical. You don't get to make decisions in between those. Is that really any different from one super-freakish hit? On the other hand, the 5 goblins do have to commit their action to attacking you. They're giving up something else they could have done. So maybe the unit action or opportunity cost has something to do with how you determine what "single" is.
In terms of the "Elements of Tactics" article I so often quote from Mr. Brian Gleichman, I prefer systems where the pace of decision -- i.e. how much time and opportunity is available to recover from any specific failure, or more simply, how fast you can lose -- has at least a little room for escape or recovery, even at its grittiest. I have always thought that in practice, even among players who mostly go the min-max power-gaming route, losing a character on which you've spent a great deal of development and game time because of a single bad roll or single uninformed choice is profoundly aggravating. However, I was wondering if other people had different perspectives on this, and where and when they considered such level of instant total risk appropriate.
I could give you a lot of different perspectives on this. I'll limit myself to 2.
First, is gamers as a whole have always been bi-polar on this topic. On the one hand, yeah, nobody wants to love their beloved character on a single freakish roll. And by the way, it's always "single" and always "freakish." To me, this kind of sounds like the lady doth protest too much. It speaks of a dire need to dodge all responsibility for your own character's fate. And so I'm often less than sympathetic. The opposite end of the spectrum usually involves a high level D&D fighter intentionally take a header off a cliff. Sort of like a short-cut. Since the player knows the character's got plenty enough hit points to survive the fall. And so the opposite belief is, you should never be so tough that you're invulnerable.
Second, I think it was Legend of Zelda I was playing when I was a kid, my godfather started making fun of it. All these hearts. The videogames he grew up on, it's one hit and you were dead. And I played those videogames, too. And they really do work just fine. Perhaps because we go in knowing that it's one hit and you're dead.
In some ways, I think those old games work even better. Because once you get used to the idea of being able to take multiple hits, a nail-biting victory becomes equated with losing most of your hits, but not quite all. And so then a good challenging adventure is one in which the player is expected to lose most of their hits. And that can be a problem. Because if you fall behind early, you might enter the latter half of the adventure not able to take the hits the good design expects you to hit. And it's not entirely clear to me that playing those second two hours with no chance of winning is something that should even be done. In baseball, if the home team is up in the bottom of the 9th, the game ends there and then. You don't continue to play things out once the end is set in stone.
Granted, it's not exactly that in an RPG. You could be destined to lose and still fight for your survival. I just question, if you can't afford to take a hit in the first encounter, what actual benefit is there to designing the RPG form such that it sets the expectation that, yes, you can take a hit without going down? Are we actually gaining something by doing this? Is your favorite character actually any safer for my leading you to believe you've got a buffer against death?
Just playing devil's advocate, really. I do take one cue from the old school video games. You usually get 3 lives. So I'm cool calibrating the RPG to 3 hits and you're done. And I guess that might translate to three bad decisions as well. However, one bad decision to fight 5 goblins will kill you just as surely. And if it's possible for one mistake to be that severe--I guess you should have known better than to take on 5 goblins by yourself--then why can't another mistake, one where it's a single but much more powerful adversary, be just as severe. In other words, why shouldn't there be one hit kills? I get there is strength in numbers. But is there not also strength in strength?
EDIT: I put this in the general RPG discussion forum because I wanted to get examples from what people have actually seen in play, but if this is a better fit for the Design and Development forum, I ask that it be moved there, with apologies for the inconvenience.
You know how in AD&D 2E, there's a massive hit rule, where if you take 50+ damage in one shot, your character has to make a system shock survival check or die? Gary Gygax's Lejendary Adventure RPG has the exact opposite rule. If you take over 50 damage from any single source, you get a special "Disaster Avoidance Check" of which there are two possible degrees of success. The lesser, you take only half damage, but there may be a complication added--broken bone, or something appropriate to the situation. The greater success, you avoid all damage completely. (For context, LA Avatars usually start with more than 50 health. It's possible to start lower, but you pretty much have to do it on purpose.)
The reason I fucking looooooove this rule is because it boxcars both ears of the bipolar gamer at the same time.
Look. You get an extra die roll. And that reduces the probability of being killed in a single hit. But there's still a chance. Don't be that jerkoff fighter leaping off a building because you're too lazy to take the stairs. And definitely don't be the guy that's going to stand toe to toe with the Titan of Infinite Strength. Because there's a chance, however small, that it will end you. Enough to be a deterrent.
The flip side of it is, imagine being the min-maxing player pumping your harm up to the high heavens. Knowing that if you deal 50 harm, you deal 50 harm, but if you deal 51 or more, you might only end up dealing 25, or even nothing, that's going to make you really not want to cross that threshold. No. We're not limiting how much harm you can do. You want to make it your obsession, you can approach +infinity harm bonus if you want. But a lot of people are going to not want. Rather than continuing to build up the amount of harm you do, it might behoove you to develop your Avatar in other directions. Like maybe focus on being able to make multiple attacks.
We still preserve the idea of a one-hit kill. That threat always exists, and it helps keep PCs humble. But we reduce both the probability of dealing such a blow as well as reducing the number of characters who ever attain the ability to deal such a blow.