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:
- 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.
- 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.
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.