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Certain effects in the game, such as the Chill Touch spell, prevent (re)gaining hit points :

On a hit, the target [...] can't regain hit points until the start of your next turn.

But can any effect in the game prevent (re)gaining temporary hit points ?

The goal is partially to find a counter to abilities that "refresh" temporary hit points on a per-round basis, like the Heroism spell or the Twilight Sanctuary Channel Divinity. Although these abilities have specific counters of their own (break concentration / dispel magic for Heroism, have the recipient be too far away from the Twilight Sanctuary), I'm wondering if any effect in the game says "this target cannot (re)gain temporary hit points for [X duration]", or otherwise indirectly prevents temporary hit points from being (re)gained.

Gael L
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    Are you trying to bypass the temp hp or just find an effect that prevents a creature from getting temp HP? Also, what is the goal with this maneuver? – NotArch Apr 27 '21 at 17:46
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    @NautArch The latter (I do know that a few effects in the game care only about your actual hit points, like Sleep or Power Word Kill). The goal is partially to find a counter to abilities that "refresh" temporary hit points on a per-round basis, like the Heroism spell or the Twilight Sanctuary Channel Divinity. Although these abilities have specific counters of their own (break concentration / dispel magic for Heroism, have the recipient be too far away from the Twilight Sanctuary), I'm wondering if any effect in the game says "this target cannot (re)gain temporary hit points for [X duration]" – Gael L Apr 27 '21 at 17:51
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    Gotcha, that's what your question is asking, but just wanted to make sure. Nice question! – NotArch Apr 27 '21 at 17:52
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    I'm voting to leave open because it is perfectly clear what is being asked. – Thomas Markov Apr 27 '21 at 18:21
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  • Does being dead prevent a creature from receiving temporary hit points? – Jon Schneider Apr 28 '21 at 20:42
  • Are you only accepting effects that have text specifically saying they prevent temporary HP or are you also interested in effects that will also prevent that? – Allan Mills Apr 28 '21 at 22:18
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    @AllanMills I do not understand your question. – Gael L Apr 29 '21 at 02:46
  • @AllanMills Please do not answer in comments. – Thomas Markov Apr 29 '21 at 17:36
  • @AllanMills I think that would be better for an answer to include if it does in fact work. Contingent methods should be coverable by a good answer. – Someone_Evil Apr 29 '21 at 18:44
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    @ThomasMarkov I'm trying not to, but I needed clarification on the question. – Allan Mills May 01 '21 at 00:06

3 Answers3

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Turn your enemy into a Swarm or an object

Several Swarms, such as the Swarm of Insects, include the following line as part of their Swarm feature:

[...] The swarm can't regain hit points or gain temporary hit points. [...]

Thus, if you were to turn somebody into a Swarm by some means, such as (true) polymorph or shapechange, they would not be able to gain temporary hit points (THP).

Similarly, turning somebody into an object will usually make them an invalid target for sources of THP and an invalid target for whatever may have already been giving them THP, such as heroism (I haven't found a source of THP where this isn't the case, as in, I haven't found a way to give an object temporary hit points). Though what exactly happens when you become an invalid target for a spell like heroism isn't entirely clear:

Exempt-Medic
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    Can you actually change into a swarm? Although they have a stat block, they aren't exactly a single creature. – Allan Mills Apr 28 '21 at 10:18
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    @Allan We have quite a few questions on the creature-ness of Swarms and the trend seems to be that to not consider them a single creature makes a mess. But feel free to look through the questions we already have and ask a new one if you think it's different enough. Here's the most general I could find, with related questions linked below it: "How are swarms considered in terms of number of creatures?" – Exempt-Medic Apr 28 '21 at 11:06
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    @Medix2 Spells that target creatures work on swarms, much like spells that target eyeballs work on (most) humans. – Yakk Apr 28 '21 at 13:09
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    @Yakk Yes, but the confusing thing isn't about spells that target creatures, it's about spells that target a single creature. And also whether or not spells that let you turn into a beast (singular) also let you turn into a swarm of which consists of multiple beasts. – Exempt-Medic Apr 28 '21 at 13:12
  • While swarms function like a single creature, their type is usually described as "Medium swarm of Tiny beasts" or similar, i.e- they are multiple smaller beasts functioning as if they were one beast for convenience (because tracking a million tiny creatures is fun for no-one). A DM could allow it anyway, but it's highly questionable in RAW I think. – Haravikk Aug 26 '21 at 19:18
  • Also worth adding that even if this did, or was allowed to, work, you cannot use Shapechange to do it as that spell can only target self, I think you mean Polymorph or True Polymorph as the only ones that can change an enemy target. – Haravikk Aug 26 '21 at 19:31
  • @Haravikk See my earlier comment responding to your first comment. For your second comment, you could always use shapechange alongside glyph of warding to have it target somebody else – Exempt-Medic Aug 26 '21 at 19:42
  • @Medix2 that would be another questionable ruling; Glyph of Warding only changes the target of a spell, but the Self restriction of a spell is its range (targeting restrictions are defined in the spell text, like "one enemy creature you can see" or such). On the swarm issue the linked question isn't about transforming into swarms, the. spells specify "a creature" but swarms are explicitly multiple in their type. – Haravikk Aug 27 '21 at 22:47
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Nothing in any of the rule books includes such an effect

To figure this out, I went to D&D Beyond to search entries that related to temporary hit points. None of the entries I saw said anything that could prevent someone from gaining temporary hit points.

There are no effects in any of these entries that actually prevent one from gaining temporary hit points. And D&D Beyond includes all sourcebooks, not just SRD ones, so I think we can pretty conclusively say there are no such effects.

Lysanderoth
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    The trouble with DNDBeyond is that the search shows a maximum of 35 entries, so all your results showing 35 are incomplete. – Thomas Markov Apr 27 '21 at 23:06
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    That said, I am thoroughly relieved that there are no vehicles that can prevent me from gaining temporary hit points. – Thomas Markov Apr 27 '21 at 23:06
  • I appreciate your extensive research ! I'll wait a bit before accepting your answer, however, in case something miraculously pops up, heh. – Gael L Apr 27 '21 at 23:23
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    As further evidence, any such effect would have bizarre consequences, such as making a creature immune to a seemingly random collection of spells and effects, including Mass Polymorph, Armor of Agathys, Motivational Speech, False Life, the Battle Master's Rally maneuver, etc. – Ryan C. Thompson Apr 28 '21 at 01:56
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    @ThomasMarkov Also, the search on D&D Beyond is really, really subpar – Olivier Grégoire Apr 28 '21 at 18:53
  • @OlivierGrégoire I actually think the search in D&D Beyond is pretty good. The problem in this case is that it's designed to find the single specific thing you're looking for, and here we are trying to find all occurrences of something. – Ryan C. Thompson May 01 '21 at 23:05
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Antimagic field will work in some cases

The antimagic field spell block some means of gaining temporary hit points. Specifically any that are magical in nature, provided the target is inside of the field.

For example, the False Life spell will be stopped from working since it is a spell and thus magical. A warlock who has Dark One’s Blessing, and reduces a hostile creature to 0 HP, will not be stopped from gaining temporary HP since that ability isn't specifically magical.

Allan Mills
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  • I think the problem here is that it doesn't actually block gaining temp HP, but blocks the spell. Too indirect? – Jason_c_o May 02 '21 at 01:16
  • @Jason_c_o False Life and Armor of Agathys only grant their temp HP "for the duration", i.e- the temp HP disappears if the spell does, so they're definitely an ongoing spell effect. So if suppressed by an antimagic field the temp HP would disappear, but would come back once you leave (unless the spell expired). – Haravikk Aug 26 '21 at 19:21