In any system where any character of note is a damage sink this is simply going to happen. Playing systems that don't feature piles of hit points to represent advanced fighting skill is a start.

Whenever you attempt to apply real world specific results in system that was designed to handle combat abstractly there will be a clash of expectations. You may be expecting the natural result of your in game action and the rules deliver what they are designed to deliver- points of damage.

There are non-abstract combat systems that model this sort of thing fairly well. If you are looking to simply resolve combat quickly handling a good number of combatants, D&D does the job just fine. If you want to dwell on the combat details, want specific logical effects of injuries, etc. use GURPS, RQ or some other detailed combat system.  Of course such systems cut both ways. Player characters can't shrug off tons of damage because they are heroes. PC's can get arrows to the throat, limbs hacked off and so forth. Such systems can be great for teaching players the consequences of entering deadly combat at the drop of a hat. It also solves the 3 guards pointing loaded crossbows at the PC warrior problem. A powerful D&D fighter just laughs at them takes 3 bolts worth of damage then proceeds to chop the guards up with barely a scratch to his mountain of hit points. Even a very skilled GURPS fighter listens to what the guards have to say.

Quote from: Exploderwizard;917386In any system where any character of note is a damage sink this is simply going to happen. Playing systems that don't feature piles of hit points to represent advanced fighting skill is a start.

Whenever you attempt to apply real world specific results in system that was designed to handle combat abstractly there will be a clash of expectations. You may be expecting the natural result of your in game action and the rules deliver what they are designed to deliver- points of damage.

There are non-abstract combat systems that model this sort of thing fairly well. If you are looking to simply resolve combat quickly handling a good number of combatants, D&D does the job just fine. If you want to dwell on the combat details, want specific logical effects of injuries, etc. use GURPS, RQ or some other detailed combat system.  Of course such systems cut both ways. Player characters can't shrug off tons of damage because they are heroes. PC's can get arrows to the throat, limbs hacked off and so forth. Such systems can be great for teaching players the consequences of entering deadly combat at the drop of a hat. It also solves the 3 guards pointing loaded crossbows at the PC warrior problem. A powerful D&D fighter just laughs at them takes 3 bolts worth of damage then proceeds to chop the guards up with barely a scratch to his mountain of hit points. Even a very skilled GURPS fighter listens to what the guards have to say.

Pretty much this.  D&D has a pool of hit points that represent two things...1. Actual wounds, 2. The Stamina to avoid damage through your skill in combat.  Obviously in a Silent Kill situation, number 2 does not apply, so if you only have one number, you have to boost the damage accordingly to represent the nullification of 2.  Hence Backstabbing doing more damage as you increase in level, representing your skill in the techniques required.

However, even as a high level thief, if you're trying to Backstab a Fighter with very high HPs, then even a Damx5 may not be enough for an Instant Kill.  You're trying to get a more granular result then the rules were meant to support.  So, you do what any good D&D GM does, you houserule it, which will depend on system.  Grant Advantage to damage dice (5e), allow Move Silently rolls to keep quiet as you keep Backstabbing through the Surprise rounds (1e).  Use a Vitality/Wounds system to replace HPs and have Backstab be not so much damage but applied directly to wounds.

Or you pick a game like Rolemaster, where Surprise will get you a bonus to hit, probably resulting in a Critical, and the Ambush skill will increase the severity of that critical.  Or Mythras, where taking a combat hit completely unawares is extremely nasty, and learning Assassination and Silent Kill techniques make it even more so.  Or Shadowrun, where the complete lack of opposed rolls and reduced target number will probably allow your number of successes to push the damage into Deadly range.  There are a lot of systems out there where the natural granularity of the system allows for "Backstabs" to just occur organically from the system without a dedicated power or skill that allows it.  D&D's just not one of them.

Quote from: Exploderwizard;917386In any system where any character of note is a damage sink this is simply going to happen. Playing systems that don't feature piles of hit points to represent advanced fighting skill is a start.

Quote from: CRKrueger;917408Pretty much this.  D&D has a pool of hit points that represent two things...1. Actual wounds, 2. The Stamina to avoid damage through your skill in combat.  Obviously in a Silent Kill situation, number 2 does not apply, so if you only have one number, you have to boost the damage accordingly to represent the nullification of 2.  Hence Backstabbing doing more damage as you increase in level, representing your skill in the techniques required.

However, even as a high level thief, if you're trying to Backstab a Fighter with very high HPs, then even a Damx5 may not be enough for an Instant Kill.  You're trying to get a more granular result then the rules were meant to support.  So, you do what any good D&D GM does, you houserule it, which will depend on system.  Grant Advantage to damage dice (5e), allow Move Silently rolls to keep quiet as you keep Backstabbing through the Surprise rounds (1e).  Use a Vitality/Wounds system to replace HPs and have Backstab be not so much damage but applied directly to wounds.

The problem is not a having a large number of hit points, or a lack of rules for bypassing them. It's a question of when to allow instant kills vs. death by cumulative damage. As has already been discussed upthread, there's already the example of instantly killing helpless victims, which has been part of D&D for a very long time. It's just that it's not typically applied to the backstab, because Gygax decided that thieves should have an increased chance of killing the victim with a backstab, but not an instant kill as with a bound or unconscious victim.

There are three other examples already written into the rules where people can instantly die, regardless of hit points:

(1) Save vs. poison (in the rules since the very beginning,)
(2) System shock (hinted at in Men & Magic, but not spelled out until AD&D 1e,)
(3) Assassination (added in Blackmoor.)

Those, plus the instant kill of helpless victims without a roll, can all be used to implement instant death in any other situation. The question is, do you really want it? Players may be in favor of it when they are the ones doing the killing, but how are they going to feel when they are the victims? The OP wants instant death to apply to any surprise attack from behind. But if that were allowed, it would be easy and reasonable for intelligent monsters in a dungeon to just sneak, make their surprise roll, instantly kill the last person in marching order, then flee and hide, repeating later. The surprise roll becomes a save vs. death, and the players will lose their adventuring party without much opportunity to prevent it. Maybe they could move even more slowly, with characters in the rear facing backwards and those on the flanks facing the sides, and two people examining the floors and ceilings?

I'm going to try a Wounds / Vitality style of hit points for my next game (Health / Grit). Backstabs will bypass Grit and directly damage Health. We'll see.

GURPS has pretty detailed and specific rules that handle such details to my satisfaction. The target gets no defense, and will be surprised, likely allowing multiple actions even if they survive the first action. But it does matter what you use, what your skills and strengths are, the target location, its armor, etc. There are major bonuses for the motionless target and taking several seconds, etc., so as the rules point out, it's usually really likely such a person is going to be taken out, but it's not automatic. And the detail of the rules makes it pretty clear what does happen, if something else happens e.g. the victim has armor the attacker didn't notice on his throat, or the victim clings to consciousness, or the attacker makes a superficial cut or fumbles or drops his knife or something. There's also a chance the guard sneezes or turns for some other noise or thought at the wrong time.

Quote from: LordVreeg;917280Personally?

We use a very low HP system, and we consider it like a coup-de-grace.  See the bottom.

This is honestly I think the best way to go if you want something more gritty and realistic. Low HP definitely works best for that kind of play I think. If it is is difficult to impossible to one hit kill people with a normal attack, then it some character getting killed because he was unaware is going to be hard without special rules for that situation or the GM ruling that it means instant death.

But if you are playing system that is more heroic, and you still want it, the stuff like coup de grace rules or just ruling it is usually fine.

Quote from: BedrockBrendan;917459This is honestly I think the best way to go if you want something more gritty and realistic. Low HP definitely works best for that kind of play I think. If it is is difficult to impossible to one hit kill people with a normal attack, then it some character getting killed because he was unaware is going to be hard without special rules for that situation or the GM ruling that it means instant death.

But if you are playing system that is more heroic, and you still want it, the stuff like coup de grace rules or just ruling it is usually fine.

It's low HP AND high damage.  Heavier armors make you easier to hit, but protection becomes vital.   PC fighter types normally don't hit 20hp until 10-15 sessions, 30 hp more like 30 sessions.  My highest PC hp right now is 48, after over a 160 sessions.  Joe fighter does NOT go into combat without his armor...
Even a little Dirk has a 2d4+9/d10 normal damage (still maxing out at 17 hp damage before any bonuses), and a medium one handed sword like a broadsword does 1d10+16/d6.
 And that's normal, before all the coup rules of critical damage, added damage, etc.  Criticals give minuses on the dividing die, and turn it from a divider into a multiplier.

We have somewhat high mortality from combat.

I like having the rules in place.  I mean, yes, you can just rule it, but since the rules sort of give expectations for how the world is supposed to work..the physics engine...I'll prefer a system that has taken the time to figure this one out.

Quote from: Baron Opal;917452I'm going to try a Wounds / Vitality style of hit points for my next game (Health / Grit). Backstabs will bypass Grit and directly damage Health. We'll see.

This is the obvious solution.

Another note mentioned in passing earlier - if this is "just a guard" then the assumption for me is he'd be low-level. Otherwise a Thief might make some kind of roll to size up his target to determine if indeed a backstab would even work against an experienced foe.

I don't have very much issue with Backstab. Modulating the powerlevel of the NPC's is fairly easy to do even on the fly.

Realistically, a knife isn't going to kill in one strike, no matter where you hit.  You'll DISABLE the target, quite easily, if you know where to strike.  At which point, in the case of a guard on a battlement, you pitch him over the edge and let gravity do the work.  Sadly, most fantasy games (including D&D) doesn't even bother simulating that.

Quote from: tenbones;917464This is the obvious solution.

Another note mentioned in passing earlier - if this is "just a guard" then the assumption for me is he'd be low-level. Otherwise a Thief might make some kind of roll to size up his target to determine if indeed a backstab would even work against an experienced foe.

I don't have very much issue with Backstab. Modulating the powerlevel of the NPC's is fairly easy to do even on the fly.

That's an interesting idea, giving the thief the ability to eye somebody and decide "this one is too alert and skilled for even me to take out in one shot." Still, a knife in the kidneys, &c.

I've found I greatly dislike assassination rolls. I think I can accept backstabs and poison being a "lethal shortcut", as it were. That's their point. But assassination feels a bit too much like an "I win" button. That's from the gut and a little play, however, and not based on any great logic and play testing.

Quote from: talysman;917448The problem is not a having a large number of hit points, or a lack of rules for bypassing them. It's a question of when to allow instant kills vs. death by cumulative damage. As has already been discussed upthread, there's already the example of instantly killing helpless victims, which has been part of D&D for a very long time. It's just that it's not typically applied to the backstab, because Gygax decided that thieves should have an increased chance of killing the victim with a backstab, but not an instant kill as with a bound or unconscious victim.

There are three other examples already written into the rules where people can instantly die, regardless of hit points:

(1) Save vs. poison (in the rules since the very beginning,)
(2) System shock (hinted at in Men & Magic, but not spelled out until AD&D 1e,)
(3) Assassination (added in Blackmoor.)

Those, plus the instant kill of helpless victims without a roll, can all be used to implement instant death in any other situation. The question is, do you really want it? Players may be in favor of it when they are the ones doing the killing, but how are they going to feel when they are the victims? The OP wants instant death to apply to any surprise attack from behind. But if that were allowed, it would be easy and reasonable for intelligent monsters in a dungeon to just sneak, make their surprise roll, instantly kill the last person in marching order, then flee and hide, repeating later. The surprise roll becomes a save vs. death, and the players will lose their adventuring party without much opportunity to prevent it. Maybe they could move even more slowly, with characters in the rear facing backwards and those on the flanks facing the sides, and two people examining the floors and ceilings?

Exactly. Automatic Death is readily available to every class (to editions that have it); it's called held or asleep (unconscious) outside of combat. With some prep even high level, high HP characters can die to this universally available form of Instant Death.

Just like thieves doing skills at the nigh magical level — move silently, hide in shadows, etc. — this is their skill set leaking into an almost lethal surprise attack. It's leaking from everyday Instant Death into a very unsure thing: combat. Is it a sure thing? No, it's not supposed to be. Because an out-of-combat sure thing is already available, this in-combat thing has to have a chance at failure.

In a lethal world as is everyone kinda has to sleep with one eye open. Making backstabs such reliable Instant Death would leave people walking with their backs hugging walls. Kinda crazy ramifications at that point.

Quote from: Christopher Brady;917477Realistically, a knife isn't going to kill in one strike, no matter where you hit.  You'll DISABLE the target, quite easily, if you know where to strike.  At which point, in the case of a guard on a battlement, you pitch him over the edge and let gravity do the work.  Sadly, most fantasy games (including D&D) doesn't even bother simulating that.

Ambush, and Surprise (if they fail), rounds readily allow you to shove someone over a battlement. Not too hard to rule a successful backstab as collapsing a lung to prevent them from screaming (as they fall over the battlement later, even!). Or you could just push, if you don't mind the screaming.

There's not much I see here that seems to need models to simulate. What formula models are you looking for?

Quote from: Baron Opal;917491That's an interesting idea, giving the thief the ability to eye somebody and decide "this one is too alert and skilled for even me to take out in one shot." Still, a knife in the kidneys, &c.

I've found I greatly dislike assassination rolls. I think I can accept backstabs and poison being a "lethal shortcut", as it were. That's their point. But assassination feels a bit too much like an "I win" button. That's from the gut and a little play, however, and not based on any great logic and play testing.

Yep. The *idea* behind Backstab is that it's not JUST that you're killing someone with a knife etc. But that you're particularly skilled at doing exactly that. So the solution seems rather simple - either the Thief in question is good enough or not. The corollaries being "Who are they attempting to Backstab?" and of course "Exactly how Good are they?"

The mechanics that exemplify this are what needs to be tinkered with as you see fit. My general notion in 5e if you go with Wounds/Health - you'll have to downgrade the Backstab dice a bit.

Assassination - it's a bit fast and loose. But most people I've encountered didn't use it as proscribed. They kinda used it as a replacement for "Backstab" with the Assassin class. As I recall the Assassination table was for you concocting a full-on plan and the percentage was based on your assumed skill vs. what you didn't know (which the DM could penalize/bonus you as they saw fit). I never had a problem with anyone using it either way for inconsequential NPC's that aren't the BIG BAD. I'd rather play it out, personally.

I ran into this multiple times in old D&D. We'd simply refer to the Assassination table to determine the outcome. Otherwise, it was simply "roll dice and see what happens". It was silly in retrospect.

In ZWEIHÄNDER, I let players either knock someone out with the Knockout! action or simply kill them if they approach an unaware (otherwise Helpless) foe. But the sword cuts both ways; although it's an option I rarely afford to enemies, I have at times let foes use it... and as the character lays gurgling in their own pool of blood - or as they spend a Fate Point to avoid a grisly end - they make their allies immediately aware of an attack.

Quote from: Opaopajr;917508Ambush, and Surprise (if they fail), rounds readily allow you to shove someone over a battlement. Not too hard to rule a successful backstab as collapsing a lung to prevent them from screaming (as they fall over the battlement later, even!). Or you could just push, if you don't mind the screaming.

There's not much I see here that seems to need models to simulate. What formula models are you looking for?

Formula?  Honestly, I've already house ruled it.  In the various editions of D&D I've run.  And in Fantasy Hero, I simply allowed Stealth to determine a multiplier.

5e:  You catch you're opponent unaware with stealth, you get the Rogue's Advantage bonus when striking, however, to 'disable' (In other words remove a target, whether by death or stabbing in the vitals like lungs, kidneys and so on) you have disadvantage on the strike.  If you do it on a surprise round, you get just get Disadvantage on the attack.

I used the hit location table from the Fighters Handbook in 2e.  3e, we had a rogue and the times the wizard was there, that one always managed to remove any target long before stealth or surprise ever mattered.