Are hit points non-fungible?

Question

There are many effects in D&D 5e which reduce a target's maximum hit points. Take for example, the Vampire's bite which contains the following rider:

The target's hit point maximum is reduced by an amount equal to the necrotic damage taken.

This phrasing is relatively easy to understand and is consistent with the rest of 5e's hit point definitions.

Now let's look at the Sword of Wounding. Its description has interesting implications when you consider the first sentence:

Hit points lost to this weapon's damage can be regained only through a short or long rest, rather than by regeneration, magic, or any other means.

The phrasing for this effect is very different from other similar effects such as the aforementioned Vampire's bite as it targets specific hit points. While this makes sense in concept and fantasy (the wounds inflicted by this sword are not easily healed), I find myself scratching my head when thinking about how this works in practice.

For example, let's say that a Troll has lost all but 15 of its hit points to varied (nonmagical) sources of damage. When those 15 hit points are subsequently lost to a Fighter wielding a Sword of Wounding, can the Troll use its Regeneration to return to 10 HP? I can see two different scenarios here:

1. Option 1 (non-fungible hit points): its "first" 15 hit points have been lost and can't be regained. Because these can't be regained, no subsequent hit points can be regained and the Troll remains at 0 HP.
2. Option 2 (fungible hit points): the "un-healable" hit points effectively function as a maximum hit point reduction, and the Troll regenerates back to 10 HP. On subsequent turns, its total hit points cannot exceed more than [its max hp - 15].

Are there any official sources which indicate how this works? Specifically, I'm interested in understanding whether hit points are fungible (i.e. they can be regained independently from one another) or otherwise.

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Some additional, opinion-based context: D&D is fundamentally a story-based game, so thematically, there's a lot of wiggle room for how this can be interpreted while remaining within the bounds of hit points as a concept. Option 1 fits with the idea that taking the last hit points constitutes the "killing blow". Option 2 fits with the idea of "death by a thousand cuts" (the other wounds can be healed to stave off death). The spirit of this question is basically asking whether the Sword of Wounding canonizes one of these interpretations, and asks if there are other rules which provide more clarity around this.

Answer 1

There are no hidden rules. HP are fungible.

Given the possible interpretations, in the absence of any text that forces us to pick the more complex interpretation, we should default to the simpler reading. We should not go out of our way to invent additional assumptions which the rules do not require in order to be coherent. (You may be familiar with this concept as "Occam's Razor".)

There are no rules that state or imply that HP are non-fungible. That is to say, all hit points are identical and interchangeable; there isn't an order to them. Your "last" HP isn't special or different from the others. We should not accept your Option #1 unless there is some specific rules text that supports or requires it, and since that text just doesn't exist, we're left to default to Option #2.

HP lost to a Wound can't be healed, but any HP lost in other ways can be, so the Sword of Wounding's damage can't "lock off" the rest of your HP. If your last HP was lost to a Wound, you can still heal all the other HP you have that weren't caused by Wounds, whether that healing comes from troll regeneration or a cure spell.

So yes, Sword of Wounding damage works kind of like reducing maximum hit points (though it does not, technically speaking, actually change your max HP). Why is it worded differently from the Vampire's ability? We can't say. But we can be aware that different books (and often different sections in the same book) are written by different authors, edited by different editors, and often not cross-checked to see if they're using consistent language.

Answer 2

Option 2

This is what the description of the sword says: “Hit points lost to this weapon's damage can be regained only …”. It does not affect hit points lost in other ways, they can be healed normally. In effect, it creates a separate class of hit points that are, if you like, non-fungible with normal hit points.

Note that this is different from lowering the hit point maximum. A lower maximum makes the character more susceptible to death from massive damage; hit points lost to the sword don’t do this.

Answer 3

It doesn't matter

The existing answers do a good job of showing that hit points are fungible (a position I agree with). I'd like to take a different approach: for the sake of argument, I'll assume that hit points are non-fungible and see if that makes any difference.

Bob is a level 1 bard with 14 Con, thus he has 10 hit points. Throughout the adventuring day, Bob takes the following damage (in order):

1. A single dart of magic missile for 2 force damage.
2. A hit from a sword of wounding for 3 piercing damage.
3. Damage from a wound from a sword of wounding for 1 necrotic damage.
4. A dagger hit for 3 piercing damage.

Bob's (presumably) non-fungible hit points now look like this (repetition intentional):

• 1 hit point flagged as lost to magic missile force damage.
• 1 hit point flagged as lost to magic missile force damage.
• 1 hit point flagged as lost from sword of wounding piercing damage.
• 1 hit point flagged as lost from sword of wounding piercing damage.
• 1 hit point flagged as lost from sword of wounding piercing damage.
• 1 hit point flagged as lost from sword of wounding necrotic damage.
• 1 hit point flagged as lost from a dagger's piercing damage.
• 1 hit point flagged as lost from a dagger's piercing damage.
• 1 hit point flagged as lost from a dagger's piercing damage.
• 1 hit point flagged as not lost.

Bob then casts healing word (1d4+3) on himself, getting an unlucky roll of 4. Per healing word, Bob regains 4 hit points. He looks at his selection of non-fungible hit points and selects the two magic missile flagged hit points and two of the dagger damage flagged hit points.

Bob's non-fungible hit points now look like this:

• 1 hit point flagged as not lost.
• 1 hit point flagged as not lost.
• 1 hit point flagged as lost from sword of wounding piercing damage.
• 1 hit point flagged as lost from sword of wounding piercing damage.
• 1 hit point flagged as lost from sword of wounding piercing damage.
• 1 hit point flagged as lost from sword of wounding necrotic damage.
• 1 hit point flagged as not lost.
• 1 hit point flagged as lost from a dagger's piercing damage.
• 1 hit point flagged as not lost.
• 1 hit point flagged as not lost.

Healing word doesn't say to regain the most recent N hit points lost. Spells do only what they say they do, so Bob can choose any four (non-sword of wounding) hit points to regain.⁺ This is true for every method of regaining hit points. When asked what his current hit points are, Bob counts each one individually and says "five" - the same result he would get with fungible hit points.

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⁺ If an argument is made that hit points are non-fungible and ordered, then healing spells (as written) still allow you to regain arbitrary hit points in any order. This leads to the absurd situation where healing word can heal any creature to full by specifically targeting their "top-most" hit point.

Answer 4

Hit points are fungible

Unfortunately a direct quote saying "hit points are a pool" doesn't exist. However, we do have evidence that the designers intend hit points to be fungible - look at this example about tracking hit points from the DMG Chapter 8:

For example, in a combat encounter with three ogres, you could use three identical ogre miniatures tagged with stickers marked A, B, and C, respectively. To track the ogres’ hit points, you can sort them by letter, then subtract damage from their hit points as they take it. Your records might look something like this after a few rounds of combat:

Ogre A: 59 53 45 24 14 9 dead

Ogre B: 59 51 30

Ogre C: 59

The designers suggest tracking only the total number of hit points, not the hit points themselves. While the rest of the rules could be read coherently with the assumption that hit points are non-fungible, this example would make little sense in that framework.

Answer 5

Hit points that cannot be recovered ... lower the maximum HP you can reach.

Treating this as a different exception to how HP works adds complication to the game with very little benefit here.

All forms of lowering your HP maximum either implicitly or explicitly explain how the HP maximum can be recovered. This one says healing via HD in a short rest, or a long rest, recovers it. The vampire states the reduction lasts until a long rest.

You should be relatively leery about treating 5e rules as if they where using keywords. There are a few spots where you have to do this (melee weapon attack is the worst one; but they include bonus action/action and a few others), but outside of those try to treat it as natural language, and err on the side of simplicity.

The failure to say the word "maximum" should not be taken as strong evidence that this is a distinct kind of effect than ones that do say "maximum". It behaves just like a "reduced HP maximum" effect, the game is simpler if it is a "reduced HP maximum" effect, and there aren't any serious balance concerns if you treat it like "reduced HP maximum" effects. So do it.

This means that Greater Restoration would also let you heal these wounds (at the cost of some diamond dust and a 5th level slot).