What is the general in-world reason or rational for why adventurers become harder to kill?

Is it the wear and tear on the body of constant traveling? The adrenaline of fighting and endorphins of getting injured? The willpower to risk death? The cortisol from the stress of survival?

All of the above?

This is a mostly unserious ponder, so don't get heated over anything. And I'm sure this has been debated to death across the decades, but the internet now sucks if you don't want to buy something from someone. And so I ask here...

If adventurers get their HP from the above then why doesn't the starving pilgrim get a few extra HP. The blacksmith, too, swings their tools expertly with a strong arm. I gotta think they'd be harder to kill.

I know full well the biggest reason for this is, above the table, that it's just a game. And I know I can create my table any way I want, but that is also above the table. What's the rationale within the worlds of DnD?

Hit Points (HP) are a measure of how difficult it is to kill or destroy a creature or an object. Damage reduces Hit Points, and healing restores them. 

Hit Points represent how difficult to kill a creature is -- the more experienced, the larger, the tougher, whatever -- more hit points means they are harder to kill.

It is not a simulation -- it is a representation.  This is why a creature that has to face four PCs has enough hit points to handle the attacks of four average PCs for at least a round or two -- they are not "physical body", they are just "how hard is this being to kill".

I actually think of HP as having more to do with morale than physical health. A level 1 PC gets overwhelmed more easily and, if they freeze up in a pivotal moment (ie get reduced to 0 hp) they could then suffer a fatal or near fatal injury. More experienced player characters keep cooler heads through the pain and the fear and stay in the fight longer. 

If you have ever trained in martial arts, boxing, wrestling, etc. - when you first start out, going for 2-3 minutes of giving 100% exertion in a round/match is completely exhausting. But the longer you train, the longer you can go, doing 8, 9, or even 10 back to back rounds/matches before becoming completely exhausted.

You have more endurance, you're better at avoiding hits, you learn how to better take hits. D&D refers to this as hitpoints.

In older versions (like 3E) there was actually a mechanic that better explained this. As a DM, you got access to charts in the DMG that allowed you to roll up full stat blocks with progression charts for NPCs like Commoners, Warriors, Adepts, etc. Interestingly, in a large city or metropolis, it was actually much easier to find an epic level (Level 20 at the time) Commoner than it was to find a level 5 wizard, due to the nature of the the multipliers in the build charts. This represented the effort that went in to competing for gold in a large city or metropolis as opposed to a backwater hamlet or village.

With 5E, we mostly have NPCs with relatively rigid stat blocks. To get a Commoner with NPC levels in that class, you have to homebrew something or just build a PC from scratch. The rules were simplified to make the game easier to pick up and play. So I view HP as "combat stamina".

Even a hardy blacksmith with no combat training would struggle against a level 1 monk who actually trained in the art of deflecting punches, absorbing damage, and counter-striking. If you think of it that way, it kind of helps suspend disbelief. It even changes the way I think about combat fluff.

Based on that framework, I visualize the attacks the way they happen in fully armed (an armored) combat, where not every attack damages flesh and bone. Some strikes dent or mangle armor. Some strikes slam against a shield so hard it staggers an opponent. Some strikes knock the wind out of an opponent, or waste their energy. Eventually, their combat stamina gets so low, that their defenses simply can't hold up, or they can't block attacks as well. They get reckless and open themselves up to crippling or lethal attacks. Or the armor weakens enough to be punctured, allowing bones to break or flesh to tear. I start describing this change when the enemy is bloodied. 

And in this instance, an NPC wouldn't have much combat stamina, because they don't have any combat experience. Maybe they've fought off the occasional raider, or wolf (trying to get to their sheep), and you can reflect that experience by giving them more HP than the average NPC if you like. But for the most part, NPCs tend to avoid conflict. Hence the need for mercenaries and adventurers.

Inversely, since adventurer's (at best) only have proficiency in a toolset that grants them one mundane labor ability, that same monk in the previous example would fail miserably to keep up with a hardy blacksmith in a competition to produce the most horseshoes. Because that blacksmith has tons of experience making those.

A dragon pounces on a peasant and lops his head off with a swipe of its claws.

For high level characters they dodged most of it but got bruised or a cut representing the damage.

Eventually at some point the high level characters luck runs out as they tire, and then they fall.

So adventures become harder to kill the same reason UFC MMA champions are harder to defeat, it is their skill at avoiding damage or getting into situations that finish them off.

Experience, increasing combat expertise, increased toughness, "whatever doesn't kill me only makes me stronger", etc.

However, at a fundamental level, it's not going to make sense if you think about it too hard. Hit Points do not make sense, and you cannot make them make sense. They are a game-mechanical and narrative device. High-level characters are hard to kill because the game wouldn't be fun if they weren't.

HP are not meat, or at least not necessarily meat. The only parts of HP that have a prescribed narrative are when you hit Bloodied (since some monster and player effects care about that value) and when you drop to zero (you've just received a telling blow serious enough to knock you out.) All the rest are abstract.

Quote from Inexorabletruth >>

In older versions (like 3E) there was actually a mechanic that better explained this. As a DM, you got access to charts in the DMG that allowed you to roll up full stat blocks with progression charts for NPCs like Commoners, Warriors, Adepts, etc. Interestingly, in a large city or metropolis, it was actually much easier to find an epic level (Level 20 at the time) Commoner than it was to find a level 5 wizard, due to the nature of the the multipliers in the build charts. This represented the effort that went in to competing for gold in a large city or metropolis as opposed to a backwater hamlet or village.

With 5E, we mostly have NPCs with relatively rigid stat blocks. To get a Commoner with NPC levels in that class, you have to homebrew something or just build a PC from scratch. The rules were simplified to make the game easier to pick up and play. So I view HP as "combat stamina".

Even a hardy blacksmith with no combat training would struggle against a level 1 monk who actually trained in the art of deflecting punches, absorbing damage, and counter-striking. If you think of it that way, it kind of helps suspend disbelief. It even changes the way I think about combat fluff.

Based on that framework, I visualize the attacks the way they happen in fully armed (an armored) combat, where not every attack damages flesh and bone. Some strikes dent or mangle armor. Some strikes slam against a shield so hard it staggers an opponent. Some strikes knock the wind out of an opponent, or waste their energy. Eventually, their combat stamina gets so low, that their defenses simply can't hold up, or they can't block attacks as well. They get reckless and open themselves up to crippling or lethal attacks. Or the armor weakens enough to be punctured, allowing bones to break or flesh to tear. I start describing this change when the enemy is bloodied. 

And in this instance, an NPC wouldn't have much combat stamina, because they don't have any combat experience. Maybe they've fought off the occasional raider, or wolf (trying to get to their sheep), and you can reflect that experience by giving them more HP than the average NPC if you like. But for the most part, NPCs tend to avoid conflict. Hence the need for mercenaries and adventurers.

Inversely, since adventurer's (at best) only have proficiency in a toolset that grants them one mundane labor ability, that same monk in the previous example would fail miserably to keep up with a hardy blacksmith in a competition to produce the most horseshoes. Because that blacksmith has tons of experience making those.

 I agree with this interpretation of hp but it is a little less fun to not actually stab or slash your enemy when you get a hit in but it is a very good explanation 

The problem with interpretations where the higher level character is harder to kill because of skill or luck is that some threats are not realistically possible to significantly mitigate with skill, and the problem of healing (10 points of healing on a first level PC will typically take them from the edge of death to full health; on a level 10 it just takes them from edge of death to severely battered. So, are you using your skill to evade the healing, and if so, why?). I recommend just assuming that higher level PCs are superhuman.

I don't have time to search it right now but it was eloquently stated in an older edition as and I'm paraphrasing:  HP represents your physical toughness which is roughly your first level HP, and also your skill and stamina as you progress in levels.  That hit you took would have killed any normal man but your skill turned into a nick or a miss.  As your HP fall, your reflexes are slowing and your supply of luck/skill/stamina is dwindling to the point where you CAN be slain like any other man.  So a Fighter with 100 HP might have 15 real hit points and 90 points of skill/luck/intuition/stamina. 

That was the original thinking anyway.

Quote from Pantagruel666 >>

The problem with interpretations where the higher level character is harder to kill because of skill or luck is that some threats are not realistically possible to significantly mitigate with skill, and the problem of healing (10 points of healing on a first level PC will typically take them from the edge of death to full health; on a level 10 it just takes them from edge of death to severely battered. So, are you using your skill to evade the healing, and if so, why?). I recommend just assuming that higher level PCs are superhuman.

 No, but healing can also be quantified in the same way.  Yes, it heals physical wounds but it can also restore some of the stamina you have lost through combat, aches and pains no longer slow your reflexes and so on.  I recommend NOT just assuming that a higher level PC is physically as durable as a dinosaur.

Quote from ArmorStorm >>

I don't have time to search it right now but it was eloquently stated in an older edition as and I'm paraphrasing:  HP represents your physical toughness which is roughly your first level HP, and also your skill and stamina as you progress in levels.  That hit you took would have killed any normal man but your skill turned into a nick or a miss.  As your HP fall, your reflexes are slowing and your supply of luck/skill/stamina is dwindling to the point where you CAN be slain like any other man.  So a Fighter with 100 HP might have 15 real hit points and 90 points of skill/luck/intuition/stamina. 

 

That was the original thinking anyway.

 This was the explanation of it when I played back in 2e. 

I had to use a similar justification for my paladin having less HP than both the cleric and rogue in the party (DM made us roll and mine were... subpar). I justified it as he had much less will to fight after getting beat on than those two. Would have been even funnier if he were an Oath of Glory.

Excellent discussion! This is exactly what I was hoping for.

I'll have specific replies later.

Repeating my assumption that this is an ooold conversation, and I don't expect to break new ground here.

Thank you!

I think it is worth noting that, since this is a fantasy adventure game, a certain degree of action movie resilience can be applied to HP as well as the more abstract stuff, particularly on high CON/hit die characters. Sure, the Wizard is still avoiding real in-universe injuries even when they’re “hit” by a dragon’s claws or breath weapon until the HP gets low, but the Barbarian could be coming away from those hits with some sweet scars to show off, even if realistically anything that cut someone up or burned them like that should land them in either a hospital for a few weeks or six feet under.

I think the actually correct answer to HP is, to (completely inaccurately) paraphrase David Mermin, "Shut up and play" -- i.e. don't try to make sense of it, just accept that the numbers are what they are. If you really want a physics simulator, use a different RPG.

When I played in 1E the reason was that X points of damage might be a slice to the bone on a 1st Lvl character, but a paper cut to a 22nd Lvl character.

The experience of a high level character has a better reaction time and knows how to move to allow less of their body to be hit.  They know how to shift so that the armor itself can absorb more of the energy/edge from a blow.  

The opposite is also why a low level category can only max out X points of damage which is not much more then the weapon itself.  But a High level character can inflict much more then X points with a similar weapon.

Look at it like football players take a freshman in high school as level one. Throw him on the Super Bowl winning NFL team in the same position and see how long he lasts.

10 hp vs 100 hp.

as it’s been said conditioning experience, knowing how to take a hit being used to taking hit wearing the gear 100% correctly instead of kind of sort of strapped in the right place all those things go to longevity.