Instakill Mechanics in TTRPGs

[Thomas Shey]

The problem with hit points and one-shot kills is that you have to have few enough hit points to be taken out by a single attack, which means few enough to get taken out by two typical hits.

Not necessarily true. I can also be a case where its harder to be nickled-and-dimed to death than be killed by a single large hit by a much larger factor.

A couple examples:

1. Early RuneQuest could take a fair number of random hits if you were reasonably armored to put you down; but a single crit to the head could do the job.

2. Things like open-ended dice rolls can generate a lot more potential damage than you'll likely do with two normal hits. You see this in Savage Worlds where there's always a potential for sudden-death, but it doesn't actually happen all that often, and unless there's a bad imbalance in damage to Toughness, getting piecemealed actually requires some work.

But a system doesn’t have to be super-lethal to allow one-shot kills, if it’s not based on a buffer of hit points. If each attack has a 1-in-10 chance of ending the fight, that’s equivalent to having 10 hit dice, in most ways, but you don’t know the first 9 attacks will fail, and the 10th will succeed.

Hmmm. I'm now wondering if you meant "hit points" in the "level elevating hit points" sense. But even there, things like open ended damage or occasionally-severe crits can still get the job done.

 

[Thomas Shey]

Any legitimately fair fight is, almost by definition, a 50-50 proposition.

I was not using “kill” in a literal sense, by the way, but as a shorthand for knocked out of combat somehow. Presumably characters could be healed, through mundane or magical means, in such a system, too.

Yeah, you can absolutely have take-outs that are non-lethal; they're the expected case in most superhero games for example.

(Though there are genre and expectaton things there that usually mean if one-shot takeouts are going to be a possibility, there's something to buffer against that, as the design of M&M shows).

 

[Edgar Ironpelt]

The problem with hit points and one-shot kills is that you have to have few enough hit points to be taken out by a single attack, which means few enough to get taken out by two typical hits.

But a system doesn’t have to be super-lethal to allow one-shot kills, if it’s not based on a buffer of hit points. If each attack has a 1-in-10 chance of ending the fight, that’s equivalent to having 10 hit dice, in most ways, but you don’t know the first 9 attacks will fail, and the 10th will succeed.

Well, that "1-in-10 chance" system does have the advantage of "The winners of a fight generally come out unscathed" falling out naturally, vs a hit point system where recovery to full hit points after every fight feels artificial, no matter how necessary or desirable it may be.

The drawback is that it's a "save or suck" system extended to combat, with all the problems, complaints, and strong incentives to apply distortions that come with save-or-suck systems.

 

[SpellObjectEnthusiast]

Well, that "1-in-10 chance" system does have the advantage of "The winners of a fight generally come out unscathed" falling out naturally, vs a hit point system where recovery to full hit points after every fight feels artificial, no matter how necessary or desirable it may be.

The drawback is that it's a "save or suck" system extended to combat, with all the problems, complaints, and strong incentives to apply distortions that come with save-or-suck systems.

Unscathed minus the members of the winning party that die, of course.

Any kind of luck-based rather than attrition based system will always result in a big pile of PC bodies - the PCs will inevitably face more attacks per campaign than any NPC, and will mathematically eventually get unlucky and die.

An attrition system gives the players an idea at the start of the fight whether they are able to handle it or should consider fleeing, based on how many resources they have left.

In a luck based system where any fight can be fatal? The only logical choice as a player is to always sneak past/flee/avoid/surrender/bribe literally every single fight. Fighting EVER is a stupid proposition, unless its literally forced on you by the GM.

 

[Gorgon Zee]

In a luck based system where any fight can be fatal? The only logical choice as a player is to always sneak past/flee/avoid/surrender/bribe literally every single fight. Fighting EVER is a stupid proposition, unless its literally forced on you by the GM.

In real life, when I drive my car, there is an element of luck where every drive might be fatal. But that doesn't mean I didn't drive my family to Origins.

At heart, this is a simple risk-reward evaluation. Is this worth fighting for? If the reward is worth the risk, then your PC will do it -- that is the logical position. It's not dependent only on the risk of death -- there are plenty more stakes that might apply.

I'm sure everyone has played a character who has risked death to "win the love of their life", or to achieve a degree of fame, or to gain a powerful item. I suspect a fair number of characters would also sympathize with William James from the Hurt Locker -- only really feeling alive when in a life-or-death situation.

Fighting for no gain, or fighting when there is a safer way to achieve the same gain is absolutely a stupid proposition. But, very often in RPGs, there isn't a better way.

 

[SpellObjectEnthusiast]

Even if the chance of death is as low as 5% - that means that after being attacked 10 times there's a 40% chance you were killed. That could happen in as few as 1-3 fights.

It's simple math - PCs face a higher chance of death than NPCs because they're in more scenes across a whole campaign. Any luck based kill system will invariable result in lots of PC deaths, unless PCs simply avoid any kind of violence.

I've seen players give up treasure, fame, magic items, or even NPC lives to save themselves, letting the problem be and seeking safer pastures. If one corner of the sandbox looks too dangerous, they go somewhere else looking for an easier reward.

Similarly, I've seen players get resentful in contained adventures where fighting is assumed at a certain point and a PC inevitably dies as a result. (You can't "go somewhere else" in a one shot).

 

[Celebrim]

Even if the chance of death is as low as 5% - that means that after being attacked 10 times there's a 40% chance you were killed. That could happen in as few as 1-3 fights.

Agreed. It's important for all humans to understand that they are instinctually bad at statistics and probabilities. It's a gap in our supposed "general intelligence".

I've been running D6 for like 4 years now, and it features the risk of instakill that in my opinion is bad for the game. But it mitigates against the problem by in practice making the chance a PC built for combat will get one shotted in the 1 in 50,000 or less range. It could happen, and if it did happen it would be bad for the game, but the relatively large dice pools and the fact everything is an opposed roll makes it really unlikely to happen. And a PC that is in trouble can usually take full defensive actions and seek cover so that even if wounded they can avoid a death spiral in most combat situations (ei, not facing a rancor or some other rare boss monster). Plus, you have quick medikit first aid usage that functionally can act like magical healing.

But it's still a problem, which the designers recognize in their introduction to combat, calling this game with a 1 in 50,000 chance of death gritty and dangerous and telling players that combat is to be avoided if possible.

 

[Thomas Shey]

In real life, when I drive my car, there is an element of luck where every drive might be fatal. But that doesn't mean I didn't drive my family to Origins.

At heart, this is a simple risk-reward evaluation. Is this worth fighting for? If the reward is worth the risk, then your PC will do it -- that is the logical position. It's not dependent only on the risk of death -- there are plenty more stakes that might apply.

The problem is that you have to have the reward be pretty massive if "fairly high probability of death" is the trade off. Having a reward that big on the even semi-regular creates its own problems.

 

[mmadsen]

1. Early RuneQuest could take a fair number of random hits if you were reasonably armored to put you down; but a single crit to the head could do the job.

If you’re unlikely to take multiple hits to the same random hit location, then it effectively comes down to a roll (the damage roll) that has to overcome a target number (the hit points at that one location), which is effectively a save against being disabled or killed.

2. Things like open-ended dice rolls can generate a lot more potential damage than you'll likely do with two normal hits.

Yes, non-linear damage moves along the continuum from traditional hit-point attrition to independent attack results.

Hmmm. I'm now wondering if you meant "hit points" in the "level elevating hit points" sense. But even there, things like open ended damage or occasionally-severe crits can still get the job done.

Realistic combat involves people fighting after taking multiple stab wounds or gunshot wounds — or dropping dead on the spot. A straight, uncomplicated hit-point system has to choose one or the other. An equally simple system with a single roll can model that variability though.

 

[Thomas Shey]

If you’re unlikely to take multiple hits to the same random hit location, then it effectively comes down to a roll (the damage roll) that has to overcome a target number (the hit points at that one location), which is effectively a save against being disabled or killed.

It was possible to take multiple hits to the same location, but only three of the seven were normally going to be lethal if it piled up high enough (in fact, an odd quirk of the system could mean that while it had bad consequences, you were more likely to get killed by accumulated damage than a single big hit to an arm or leg).

The real trick was that when fighting other human sized opponents, barring a crit you had a lot of time to figure out things were going badly before you were disabled or killed, and potentially do something about it. This was probably partly a consequence of the fact it wasn't an all-or-nothing damage system like the D&D sphere.

Yes, non-linear damage moves along the continuum from traditional hit-point attrition to independent attack results.

Yeah, that's even true with accumulated damage being a thing.

Realistic combat involves people fighting after taking multiple stab wounds or gunshot wounds — or dropping dead on the spot. A straight, uncomplicated hit-point system has to choose one or the other. An equally simple system with a single roll can model that variability though.

That's actually sort-of true and sort-of not. While people can end up fighting through a lot of wounds (and not really even noticing it until the battle is over and the adrenaline has subsided) and sometimes die of shock or bloodloss right in the middle, passing out because of bloodloss or shock is also entirely possible. Its one reason the presence of combat medics on the battlefield can make a considerable difference in modern warfare. Being insta-killed with small arms is surprisingly rare, even moreso once you exclude blood loss situations.