D&D 5E Hit Point Maximum Damage House-Rules

[Stormonu]

Not a fan of this, but if you're going to use this I would consider changing the Hazard damage to half against max HP, the other half to regular HP. Maybe so far as it only going against max HP if any relative save is failed.

I'm assuming that if someone's max HP is reduced to 0 they can't recover - does that mean they're dead? How would this work with resurrection-style magic, if at all?

 

[Tales and Chronicles]

I think I'd keep it occasional and not on every attack or failed save.

Maybe a new, un-blockable, damage type dealt to Max HP and current HP? Something like Lethal or Wounding or something like that.
So a failed save against a Poison effect deals Wounding damage instead. Fall damage and traps could deal Wounding damage. A Disease or Curse could deal 1d6 Wounding damage each hour/day. Critical hits change the damage dealt to Wounding instead of its normal damage. Features like Evoker's Overchannel or Berserker's Frenzy could deal Wounding damage instead of Exhaustion or necrotic damage. Vampire natural attacks could deal Wounding damage, to go back to ye' ol' level drain.

etc

One nice effect it would have would be to leave the Long Rest recovery as is, but make the recovery of Max HP only possible through a Downtime Activity. So your characters can go back to max health over a long rest, but their maximum health will be drained, so you wont be top shape.

 

[Stalker0]

I think the big elephant in the rule is how the max HP gets restored....without knowing that, its hard to really guage how intense this rule is.

I will say, I don't think you could go with the full damage of a spell reduces your max hps, even half damage on a fireball sounds crippling to me, but again that depends on the max HP recovery. I'm envisioning one fight leading to several days of rest kind of thing.

Since you mentioned Wound/Vitality....I will say that to me the thing that broke the system was all the ways to attack wounds: Sneak Attacks and Crits especially. The system otherwise is great, but it lead to scenarios where high level characters were getting butchered by schlubs just hoping for crits, which effectively removed vitality from the board.

 

[Maxperson]

I've seen reduction to HP max done two ways, curious which way you are applying it.

A PC had 50 maximum HPs and currently is down 10 to 40 HPs. They take 5 points off their maximum reducing it to 45. Do their current HPs stay the same because it's still lower than max HPs, or do you track "they are down 10" and stay with the same damage taken so it also reduces their current HPs to 35?

From his examples in the OP his possibility number 1 was your first experience.

"#1. You are hit by a fireball for average 28 damage and fail the saving throw. Your hit point maximum is reduced by half the damage, to 36 (50-14), and your hit points by the full amount, to 22 hit points (50-28). So, you have 22 / 36."

Then his possibility number 2 was different from your second experience with damage only coming off of max hit points. I'm not fond of that one.

"#2. You are hit by a fireball for average 28 damage and fail the saving throw. Your hit point maximum is reduced by 28 points to 22 (50-28). Since your current hit points cannot exceed your hit point maximum (without temporary hit points, that is), your hit points are also reduced by 28 to 22.
Note: If you were already injured and your current hit points were at 15 (for example), they would not be reduced further with this option."

Personally, I wouldn't do it the second way you've seen it done. That seems to make damage 50% more potent, which would cause a lot of TPKs. Creatures are designed to do a lot of damage.

 

[Stalker0]

One way to go that I think is fairly simple but also reduces the impact of this rule is:

"Whenever you fail a saving throw, your max hp is reduced by the number of damage die".

So an 8d6 fireball does 8 max hp damage. That ensures you don't get confused between the half damage of a fireball on a successful save vs the half damage of a fireball on a failed save. It also means the reduction is more graceful, players get ground down but they don't get shattered by one bad save.

 

[Steampunkette]

Secondary support rules:

Cure Wounds and Healing Word restores your Max HP by the spell slot level. Use it at 1st level you get 1 Max HP back. Cast it at 5th and you get 5. Same goes for Mass Healing Word and Mass Cure Wounds, but everyone targeted gets their Max HP back.

Regenerate restores Max HP equal to the regular HP restored.

Heal restores full Max HP. As does Mass Heal.

Long Rests recover your Proficiency Modifier in Max HP.

Healing Potions recover your Proficiency Modifier in Max HP.

And, of course the following rule applied to everyone but the PCs:
Anything that deals damage in d4s now deals d2s.
Anything that deals damage in d6s now deals d4s.
Anything that deals damage in d8s now deals d6s.
Anything that deals damage in d10s now deals d8s.
Anything that deals damage in d12s now deals d10s.

Because in this system Magical Healing needs to slightly outpace incoming baseline damage since practically every fight is going to see Max HP reductions for multiple party members and this system DRASTICALLY FAVORS MONSTERS who don't bother recovering HP ninety nine times out of a hundred.

 

[Brotton Goodfellow]

I really like the idea of screwing with HP max if the damage dealt is poison or necrotic.

I’ve just had the idea of using the loss of HP max to reflect being wounded from taking 10+ points of any type of damage or dropping to zero HP.

 

[el-remmen]

My immediate curiosity is how this intersects with damage sources that already do damage to your max, like the touch of a wight. In theory it would not have to be changed at all, but if you want it to be different and scary compared to baseline damage and baseline now does damage to your MAX as well, it'd need adjusting.

For example, in my game energy draining damage from your max can only be recovered with an "Extended Rest" (a week of long rests in a safe and comfortable place) or healing magic applied while caster and target are on sacred ground (like a temple).

 

[Steampunkette]

My immediate curiosity is how this intersects with damage sources that already do damage to your max, like the touch of a wight. In theory it would not have to be changed at all, but if you want it to be different and scary compared to baseline damage and baseline now does damage to your MAX as well, it'd need adjusting.

For example, in my game energy draining damage from your max can only be recovered with an "Extended Rest" (a week of long rests in a safe and comfortable place) or healing magic applied while caster and target are on sacred ground (like a temple).

I mean... On the one hand I get it, on the other hand they're still terrifying. MORESO in this system.

You can lose max HP from a few different things that steals some of your luck. But those things? Wights JUST STRAIGHT DO IT. Every hit screws you up on top of the other potential sources you might already be suffering from.

 

[GMforPowergamers]

for a campaign I would love it... overall for every campaign I wouldn't.

having said that I play around with (off your perm hp) and (level of exhaustion) and (ability damage) a lot when I want to make scary monsters.