Negative Equivalent for Temporary Hit Points

[Arkhios]

Hello again my fellow Giants. I've met a dilemma:

Disregarding the question "why would you have negative equivalent for temporary hit points" I would like to know how should I implement an effect like that?

The way I see Temporary Hit Points, it's kind of a "damage absorption" layer.
Would a negative effect be a "healing absorption" or something entirely different?

[Fishyninja]

Is this for a campaign setting, it says to me if you are going into negative HP then the character is either dead or becoming undead?

I feel we need a little more background in order to help. Will be more than happy to put forward ideas.

[Arkhios]

Is this for a campaign setting, it says to me if you are going into negative HP then the character is either dead or becoming undead?

I feel we need a little more background in order to help. Will be more than happy to put forward ideas.

It seems you're not aware of what Temporary Hit Points are.

THP are something that you have on top of your current/maximum hit points, which are reduced before your current hit points.

So in essence, I'm trying to figure out an effect that would do the opposite, in a negative meaning.

[Fishyninja]

It seems you're not aware of what Temporary Hit Points are.

THP are something that you have on top of your current/maximum hit points, which are reduced before your current hit points.

So in essence, I'm trying to figure out an effect that would do the opposite, in a negative meaning.

I'm aware what THP are, I also understand you are not concerned with Why you would need a negative way to do it but how. I feel that we need a background into why you are asking for a mechanic for negative THP that is all.
As I stated previously as far as I am aware, however if I am wrong please correct me, when a character hits 0 hit points they are unconcious and have to make Death saves. Also if you go above a certain damage level when unconcious it could kill you correct?

Therefore are you looking for a system similar to this or something different?

[tieren]

I would have the effect reduce current maximum hp, and as the effect dissipates current max hp would increase (not necessarily actual hp unless there were an accompanying heal effect.

[Naanomi]

That's just damage that can't be healed for a certain duration... or perhaps a 'buffer' that wastes healing efforts before HP actually comes back... not sure the system really needs it but it wouldn't be hard to implement

[Hrugner]

I would assume such an effect would reduce the target's total available hitpoints preventing them from recovering lost hitpoints equal to their negative temporary hitpoints. So, a player with 20HP and 5 negative temporary HP would still have 20HP. If he took 10 damage, then he would still have the expected 10HP remaining. If he were then healed for 6HP, he would only have 15HP. The negative HP wouldn't stack with similar effects, but it could be healed with temporary hitpoints.

You could also just let the negative HP change their HP to their modified total, effectively doing damage. You could also set all "at 0 HP" effects to trigger when they've hit their temporary hitpoints. That may be a cleaner method.

I'm not sure what purpose this would serve. Using it as a trigger for other effects could be interesting.

[Arkhios]

I'm aware what THP are, I also understand you are not concerned with Why you would need a negative way to do it but how. I feel that we need a background into why you are asking for a mechanic for negative THP that is all.
As I stated previously as far as I am aware, however if I am wrong please correct me, when a character hits 0 hit points they are unconcious and have to make Death saves. Also if you go above a certain damage level when unconcious it could kill you correct?

Therefore are you looking for a system similar to this or something different?

Oh, right...
No, I mean an effect that could befall to you even while you still had hit points left, not something that would affect you at and/or below 0 hit points.

To clarify, the reason why I'm asking this, is that I'm designing a class that has an ability to give an amount of temporary hit points to a target of choice, and a sub-class would have an an ability that would essentially do the opposite.

[georgie_leech]

I can think of two ways to implement this. The first is to have 'damage' that goes away after a duration. Like, if you have 5 -THP, it's like you have 5 less health than you actually do for however long it lasts. This is the way that reverses the 'THP as vitality' perspective. That is, the same way that THP make you feel tougher than you are, -THP make you feel weaker than they are.

The other is a little more abstract, but a bit more of a mechanical parallel. In broad terms, THP acts more like a damage buffer than actual HP. Like, you can't give a dying character THP to wake them up and make them succeed on Death Saving Throws. So if you have 5 THP and take 7 damage, you use up those THP and take 2 actual damage. -THP would do the reverse: if you have 5 -THP and you took 7 damage, those -THP get used up and you take 12 actual damage.

From here, you can either have the -THP act all at once, or on a 1-to-1 basis like regular THP. The advantage of the former is ease of book keeping. They are a one and done effect, that behaves like a boost to the next hit taken. The latter is more true to the idea of them being a reverse of THP, but require a little more book keeping. Say you were hit for 7, but you had 10 -THP. Each point of damage is boosted by one of the -THP, so you take 14 actual damage, and there are still 3 -THP left over. This acts like temporary vulnerability. Which you prefer is up to you, and there's no reason it has to be all or nothing. Maybe some effects use the first way and some use the other. Whatever works.

[Fishyninja]

I would assume such an effect would reduce the target's total available hitpoints preventing them from recovering lost hitpoints equal to their negative temporary hitpoints. So, a player with 20HP and 5 negative temporary HP would still have 20HP. If he took 10 damage, then he would still have the expected 10HP remaining. If he were then healed for 6HP, he would only have 15HP. The negative HP wouldn't stack with similar effects, but it could be healed with temporary hitpoints.

So you are using it almost like a time based damage system for example a poison which takes time to inflict damage?

[BRC]

Wraith's have an effect that effectively reduces max HP, I've used that to account for things like sickness, travel fatigue, ect. But you already know that, so that's not what you're going for.

If we're thinking of Temp HP as a "Damage buffer", and Healing as the opposite of Damage.
I mean, I guess the way to think of it would be damage that has to be healed twice, and must be healed first.

So, take 10 damage, plus 10 "Antihealth". Antihealth doesn't affect hit point totals, but any healing effect must first remove Antihealth.

[Naanomi]

In practice it will just be its own (unresistable?) damage type in 90% of cases, really only shining against players themselves.

I'd be careful allowing it to take someone to 0, a damage type able to basically bypass death saves (and a few race/class abilities) to me feels problematic

[Arkhios]

I don't mind if the rule is a bit more on the abstract side, since hit points in D&D are an abstraction anyway.

[IShouldntBehere]

Implementation A "Drain": -THP as Maximum Hit Point reduction. Represents a characters maximum levels of health & energy temporarily being capped. Possible sources: Undead, Toxins, magic effects.

"Drain is a form a damage which reduces a characters maximum hit points. When a character takes drain damage their maximum hit points are reduced by an amount equal to the damage. Drain doesn't stack if a character takes additional damage if the drain would be greater than current drain their drain is increased to the amount of the damage dealt, otherwise their drain stays the same. Unless otherwise specified drain lasts 1 hour."

Implementation B "Corruption": -THP as "Anti-Healing Buffer". Represents something affecting a character that is pushing healing out of their system, slowing recovery. Possible sources: Fiends, Curses, Environment. o

"Corruption is a form of damage which reduces a charater's capacity to heal. When a character takes Corruption damage, they also gain that much corruption. Whenever a character with 1 or more points of corruption would be healed, instead remove that much corruption. If all corruption is removed any excess healing is not applied to damage unless otherwise specified. Corruption lasts until removed"

Implementation B "Bruising": -THP as "Temporary Damage". Represents things that knock the wind of out of a character, and may render them unconcious but that don't represent any long-term bodily harm. Possible sources unarmed attacks, blunted weapons.

"Bruising is a form of damage that wears off after time. Note brusin damage the character takes separately. After 1 minute bruising damage is automatically healed."

[Human Paragon 3]

For the sake of this post I'll call it "fatigue points" but you should come up with something that fits the flavor of your character class.

Fatigue Points would be a pool of damage-like points that a creature gains when targeted by the ability. It has nothing to do with their HP total or current damage, it's more like a form of separate damage.

When a creature's fatigue points =/> their current HP, they fall unconscious just as if their HP were reduced by 0.

Fatigue points from multiple sources overlap (do not stack).

Fatigue points are not affected by healing magic. Instead, they go away whenever the character completes a long rest.

[Fishyninja]

Oh, right...
No, I mean an effect that could befall to you even while you still had hit points left, not something that would affect you at and/or below 0 hit points.

To clarify, the reason why I'm asking this, is that I'm designing a class that has an ability to give an amount of temporary hit points to a target of choice, and a sub-class would have an an ability that would essentially do the opposite.

Ah I missed this post my apologies, I think everyone who has commented with Drain or Fatigue points seem to have the best idea so far.

[Arkhios]

Implementation A "Drain": -THP as Maximum Hit Point reduction. Represents a characters maximum levels of health & energy temporarily being capped. Possible sources: Undead, Toxins, magic effects.

"Drain is a form a damage which reduces a characters maximum hit points. When a character takes drain damage their maximum hit points are reduced by an amount equal to the damage. Drain doesn't stack if a character takes additional damage if the drain would be greater than current drain their drain is increased to the amount of the damage dealt, otherwise their drain stays the same. Unless otherwise specified drain lasts 1 hour."

Implementation B "Corruption": -THP as "Anti-Healing Buffer". Represents something affecting a character that is pushing healing out of their system, slowing recovery. Possible sources: Fiends, Curses, Environment. o

"Corruption is a form of damage which reduces a charater's capacity to heal. When a character takes Corruption damage, they also gain that much corruption. Whenever a character with 1 or more points of corruption would be healed, instead remove that much corruption. If all corruption is removed any excess healing is not applied to damage unless otherwise specified. Corruption lasts until removed"

Implementation C "Bruising": -THP as "Temporary Damage". Represents things that knock the wind of out of a character, and may render them unconcious but that don't represent any long-term bodily harm. Possible sources unarmed attacks, blunted weapons.

"Bruising is a form of damage that wears off after time. Note brusin damage the character takes separately. After 1 minute bruising damage is automatically healed."

These are all great suggestions (also, fixed Implemention C "Bruising", assuming that was what you meant).

The effect in question would actually be related with morale, and thus the method would be a type of fear. Which one, if any of the above, would you consider best for a drop in morale?

The "Oh my gods, we won't make it!" -kind of mentality in the face of impending doom. The will to fight temporarily reduced. In a way, remaining hit points can represent how willing you are to fight. The more hit points you have, the more eager you are (e.g. Barbarian) and the less hit points you have, the less willing you are (e.g. Wizard)

As previously mentioned, hit points are an abstraction. Also, it's worth mentioning that hit points ≠ health.

[Naanomi]

Are people immune to fear or the like going to ignore this 'damage type'?

[Arkhios]

Are people immune to fear or the like going to ignore this 'damage type'?

I would say yes. Also, since it would be a fear effect, people who get advantage on saves against fear would benefit from it as well. The effect would have a Wisdom saving throw, like the Fear spell has, though it wouldn't be magic.

[Arkhios]

I decided to go with the reduced current and maximum hit points, which would be regained once the effect ends. It's simple and effective.

[Naanomi]

I decided to go with the reduced current and maximum hit points, which would be regained once the effect ends. It's simple and effective.
What happens if someone is reduced to 0? Can they still make death saves?

[Arkhios]

What happens if someone is reduced to 0? Can they still make death saves?

I would say that if they normally would have hit points left, they just fall unconscious, but are stable while the effect lasts. If the damage that reduced them to 0 hit points is equal or more than the reduction, they start making death saves as normal.

PS. If someone's interested what class I'm designing, you can find the Homebrewery link from my signature (Warlord), and the corresponding thread in the GiantITP Homebrew sub-forum.