The 2024 version of the Periapt of Wound Closure states in its "Natural Healing Boost" feature:

Periapt of Wound Closure

Whenever you roll a Hit Point Die to regain Hit Points, double the number of Hit Points it restores.

Question 1: Does this effect apply to the Lifedrinker invocation's HP restoration, including the Constitution modifier?

Lifedrinker

Once per turn when you hit a creature with your pact weapon, you can deal an extra 1d6 Necrotic, Psychic, or Radiant damage (your choice) to the creature, and you can expend one of your Hit Point Dice to roll it and regain a number of Hit Points equal to the roll plus your Constitution modifier (minimum of 1 Hit Point).

Question 2: Does the third benefit of Remarkable Recovery (from Tal'Dorei Campaign Setting Reborn) add the Constitution modifier to HP restored by the Durable feat's "Speedy Recovery"?

Remarkable Recovery

Whenever you regain hit points as a result of a spell, potion, or class feature (but not this feat), you regain additional hit points equal to your Constitution modifier (minimum of 1).

Durable

Speedy Recovery. As a Bonus Action, you can expend one of your Hit Point Dice, roll the die, and regain a number of Hit Points equal to the roll.

Sub-Questions:
a) Are feats (e.g., Durable) considered "class features" for Remarkable Recovery?
b) If yes, would the Periapt of Wound Closure also double the total HP restored (Hit Die + Constitution modifier)?

1. Yes. The Periapt says "when you roll a Hit Point Die to regain Hit Points", and Lifedrinker is telling you to roll a Hit Point Die to regain Hit Points, so there's no reason it wouldn't apply.

2. Remarkable Recovery is from a third-party source that predates the updated version of Durable from the 2024 PHB, so I'm not sure there's a clear RAI answer, but I would say that under RAW it does.

a. I think so, yes. Keep in mind that when Remarkable Recovery was written, the only way that it was possible to get a feat was through a class feature (the 2024 concept of getting a feat from your Background didn't exist yet) and so it was reasonable to assume that feats fell under the general heading of class features. In considering adapting Remarkable Recovery to the 2024 rules, I think I would rule that feats should be included regardless of their source.

It seems clear that the intent of Remarkable Recovery is that feats should be included as class features, since it bothers to exclude itself by saying "(but not this feat)". That wouldn't be necessary if Remarkable Recovery itself didn't count as a class feature.

b. I don't see why not.

1. It would work like a crit -- the Periapt would double the roll of the Hit Die, but not the CON mod. The wording on the Periapt specifies that it's doubling the die roll itself

2. The "but not this feat" caveat makes it pretty clear that Remarkable Recovery treats feats as class features
2b. As Remarkable Recovery doesn't involve rolling any Hit Dice, the Periapt would have no effect on it

This conversation got me thinking.

Before the 2024 rules, was a feat always considered a class feature (or at least in the core rulebooks)? IMO they were separate concepts.

And now? As @wagnarokkr mentioned: "the only way that it was possible to get a feat was through a class feature (the 2024 concept of getting a feat from your Background didn't exist yet) and so it was reasonable to assume that feats fell under the general heading of class features."

So I think, under the 2024 rules, feats and class features are again separate things.

(PS. We had the Variant Human in 2014)

EDIT: adding my own answers for the questions :D

Quote from AntonSirius >>

1. It would work like a crit -- the Periapt would double the roll of the Hit Die, but not the CON mod. The wording on the Periapt specifies that it's doubling the die roll itself

2. The "but not this feat" caveat makes it pretty clear that Remarkable Recovery treats feats as class features
2b. As Remarkable Recovery doesn't involve rolling any Hit Dice, the Periapt would have no effect on it

Thank you for clarifying! To follow up:

1. Regarding Short Rest Healing:
   The Sage Advice Compendium (SAC) implies the Periapt of Wound Closure significantly benefits short rests. Since short rest HP recovery includes Constitution modifiers per RAW:

   Short Rest

   Spend Hit Point Dice. You can spend one or more of your Hit Point Dice to regain Hit Points. For each Hit Point Die you spend in this way, roll the die and add your Constitution modifier to it. You regain Hit Points equal to the total (minimum of 1 Hit Point). You can decide to spend an additional Hit Point Die after each roll.

   Does this suggest that RAI, the phrase "the number of Hit Points it restores" in the Periapt's description should encompass the Constitution modifier?

2. Synergy Between Remarkable Recovery & Durable:
   If Durable's Hit Point Dice roll (via "Speedy Recovery") receives a Constitution modifier from Remarkable Recovery, would this added modifier be doubled by the Periapt?

Whenever you roll a Hit Point Die to regain Hit Points, double the number of Hit Points it restores.

Going by the text of the Periapt, it only doubles the Hit Point Die value, as the text refers to "it", the Hit Point Die.

Quote from Voras >>

Whenever you roll a Hit Point Die to regain Hit Points, double the number of Hit Points it restores.

 

Going by the text of the Periapt, it only doubles the Hit Point Die value, as the text refers to "it", the Hit Point Die.

Thank you for the analysis! To clarify the ambiguity in the wording:

Interpretation of "it":

1. Option 1: "It" refers strictly to the Hit Die roll (e.g., rolling a 4 → 8 HP).
2. Option 2: "It" encompasses all HP restored through rolling a Hit Die, including modifiers (as hinted in the Sage Advice Compendium).

Is the Periapt of Wound Closure being an uncommon item an error? It's awfully good for an uncommon item.
Jeremy Crawford: It is a great item, but it's situational. If you never get dropped and rarely take short rests, the item is just handy insurance.

Jeremy's comment is on the item being uncommon for effectively doubling the number of hit dice.

If the wording meant all hit points, the text should read

"Whenever you roll Hit Point Dice to regain Hit Points, double the number of Hit Points restored."

The "it" is singular term, so it should not encompass all hit points.

Quote from Argenix >>

Does this suggest that RAI, the phrase "the number of Hit Points it restores" in the Periapt's description should encompass the Constitution modifier?

Do you think doubling just the result of the dice would not "significantly benefit short rests"?

The wording on the Periapt is very clear. It only doubles the dice

Quote from AntonSirius >>

Quote from Argenix >>

Does this suggest that RAI, the phrase "the number of Hit Points it restores" in the Periapt's description should encompass the Constitution modifier?

 

Do you think doubling just the result of the dice would not "significantly benefit short rests"?

The wording on the Periapt is very clear. It only doubles the dice

 I think so.

If doubling only the Hit Die (excluding Con mod) aligns with SAC calling it "awfully good for an uncommon item" and Jeremy Crawford's "great but situational" remark (assuming dependency on short rests), wouldn't excluding modifiers reduce its impact in typical short rest scenarios?

RAI Ambiguity:
Given Jeremy's vague reference to "situational" utility without explicitly addressing modifiers, could there be an intended-but-unwritten interaction with Constitution-based healing?

This distinction seems critical for understanding the item's true power level. Would appreciate any additional insights!

Quote from Argenix >>

Quote from AntonSirius >>

Quote from Argenix >>

Does this suggest that RAI, the phrase "the number of Hit Points it restores" in the Periapt's description should encompass the Constitution modifier?

 

Do you think doubling just the result of the dice would not "significantly benefit short rests"?

The wording on the Periapt is very clear. It only doubles the dice

 I think so.

If doubling only the Hit Die (excluding Con mod) aligns with SAC calling it "awfully good for an uncommon item" and Jeremy Crawford's "great but situational" remark (assuming dependency on short rests), wouldn't excluding modifiers reduce its impact in typical short rest scenarios?

RAI Ambiguity:
Given Jeremy's vague reference to "situational" utility without explicitly addressing modifiers, could there be an intended-but-unwritten interaction with Constitution-based healing?

This distinction seems critical for understanding the item's true power level. Would appreciate any additional insights!

You seem to be searching really hard for some support for your position, but it's just not there

The wording on the Periapt simply isn't vague or ambiguous, and makes no reference to modifiers, or total healing, whatsoever

Whenever you roll a Hit Point Die to regain Hit Points, double the number of Hit Points it [the Hit Point Die] restores.

As others have said, the periapt definitely only doubles the dice.

As for Remarkable Recovery -- this is an example of what happens sometimes when something is written by a third party.  The words that were chosen were not quite precisely what was obviously intended and so following a strict RAW interpretation causes this feature to not quite function correctly.

The problem with the wording is the insinuation that a Feat is a Class Feature.  A Feat is not a Class Feature.  Not in the 2014 rules, nor in the updated 2024 rules.  Feats fall under their own category of game features.

By default, a character follows the general rules of the game.  In addition, that character will also gain access to many specific game features that create additional rules or override general rules.  They also often provide rules for accessing a resource that was previously inaccessible and provide rules for using that resource.  These specific game features include:

(Background Features kind of existed in the 2014 version as a "soft feature" of sorts.  This mechanic has pretty much been eliminated in 2024.)

-- Species Traits, which come from your Species and Subspecies / Lineage.  These are specific to your Species and are described within your Species description.

-- Class Features, which come from your Class and Subclass.  These are specific to your Class and are described within your Class description.

-- Feats.  These are not specific to your Class or Species, and they are described in their own section of the rules.  Your Background or Species or Class might have a rule that grants access to a Feat, but the Feat itself has its own rules that a character uses in order to use that Feat.  For example, a character might have a Class Feature that is described within their class description which fully describes one method for casting a particular spell.  This same character might also have access to a Feat which is described in its own section of the rules which fully describes another method for casting the same spell.  The character would choose between using the Class Feature or using the Feat when casting that spell.  

-- Spells.  Spells are also not specific to your Class or Species, even if they happen to only be listed in one class's spell list for now.  The spell descriptions themselves are contained within their own section of the rules and exist independently of your Class.  The character might have a Class Feature that is described within their class description which fully describes one method for casting this spell, but the rules for resolving the spell itself are contained within that spell's description, written in its own section of the rules.  Spells are their own category of game feature to which a character might have access.

-- Magic Items and other equipment.  Magic Items and other equipment are also not specific to your Class or Species, even if they have prerequisites that they may only be used by that Class or Species.  The item descriptions themselves are contained within their own section of the rules and exist independently of your Class.  The rules for resolving the usage of such an item are contained within that item's description, written in its own section of the rules.  It's another category of game feature to which a character might have access.

When terminology is used loosely and something is referred to as a "Class Feature" in a "well, you know what I mean" sort of way, that only leads to problems and confusion such as the one in the OP for this thread.

I read the description as allowing the CON modifier to be doubled, since that is part of the hit point dice hit point recovery calculation. But if a player insisted on not doubling the CON modifier, I'd allow it. I also don't feel strongly enough about this to say much more than that in my defense.

How do we know that the "it" in the sentence isn't referring to the periapt itself?

Quote from TexasDevin >>

I read the description as allowing the CON modifier to be doubled, since that is part of the hit point dice hit point recovery calculation. But if a player insisted on not doubling the CON modifier, I'd allow it. I also don't feel strongly enough about this to say much more than that in my defense.

Yeah, I don't think it's a huge deal if a DM did rule any mods got doubled, it's just not how the Periapt is worded

"It" has to refer to something, and the only thing that makes sense grammatically is the Hit Die previously mentioned in the sentence -- not the ability/feature that includes rolling a Hit Die, and not the entire calculation

Quote from Argenix>>

Question 1: Does this effect apply to the Lifedrinker invocation's HP restoration, including the Constitution modifier? 

Question 2: Does the third benefit of Remarkable Recovery (from Tal'Dorei Campaign Setting Reborn) add the Constitution modifier to HP restored by the Durable feat's "Speedy Recovery"?

Sub-Questions:
a) Are feats (e.g., Durable) considered "class features" for Remarkable Recovery?
b) If yes, would the Periapt of Wound Closure also double the total HP restored (Hit Die + Constitution modifier)?

1. Yes they should work together.

2. No Durable is not a Class Feature, it's a Feat.

A. No Record Class Features state class features are detailed in that same chapter.

B. No

Quote from Plaguescarred >>

A. No Record Class Features state class features are detailed in that same chapter.

That's a good catch.  Here is that rule:

Record Class Features

Look at your class’s feature table in chapter 3, and write down the level 1 features. The class features are detailed in that same chapter.

Quote from Plaguescarred >>

Quote from Argenix>>

Question 1: Does this effect apply to the Lifedrinker invocation's HP restoration, including the Constitution modifier? 

Question 2: Does the third benefit of Remarkable Recovery (from Tal'Dorei Campaign Setting Reborn) add the Constitution modifier to HP restored by the Durable feat's "Speedy Recovery"?

Sub-Questions:
a) Are feats (e.g., Durable) considered "class features" for Remarkable Recovery?
b) If yes, would the Periapt of Wound Closure also double the total HP restored (Hit Die + Constitution modifier)?

1. Yes they should work together.

2. No Durable is not a Class Feature, it's a Feat.

A. No Record Class Features state class features are detailed in that same chapter.

B. No

 This is also my interpretation. EDIT: just to clarify from my side, in my opinion, for answer 1, the CON modif shouldn't be included twice.

And answer 2 and A are indeed related to the question I asked earlier.

Quote from TarodNet >>

Quote from Plaguescarred >>

Quote from Argenix>>

Question 1: Does this effect apply to the Lifedrinker invocation's HP restoration, including the Constitution modifier? 

 

1. Yes they should work together.

 

 This is also my interpretation.

I am very curious as to how you arrive at the conclusion that the CON modifier also gets doubled

It's basic algebra. If the formula is x + y, and you double X, the formula becomes 2x + y, not 2(x + y)

The Constitution modifier shouldn't be doubled, you double the number of Hit Points the Hit Die rolled restores then add the modifier .

Ha i see now, I misinterpretated the part saying "including the Constitution modifier" to mean = plus your Constitution modifier. Not that it would also double it.