Does reduction of maximum hit points stick to the form it is applied to?

Question

Following up on How does Max-HP reduction affect wild-shaped/polymorphed creatures?, which states:

Damage taken in animal form doesn't affect your original form's HP unless you're dropped to 0 HP in animal form and there's excess damage. Nowhere is it suggested that max-HP reduction would work any differently. Because Wild Shape/Polymorph gives you a new pool of HP, only that pool is affected by the reduction.

Context

A druid gets seduced by a succubus. They kiss while the druid is in bear form – this is not hypothetical as yesterday exactly this had happened. The druid gets lowered Maximum Hit Points because of this creature effect. So according to the linked Q&A, the reduction would only apply to the bear form.

Question

If the druid reverts back to normal, the HP reduction is not active anymore. What if the druid wild shapes another time, back into a bear: does it get a fresh "pool of HP", or does the Reduced Max HP stay with its bear form until it gets "cured"?

In other words: are shapeshifters actually really resilient against abilities that reduce maximum hit points?

Example

In case it helps to clarify, let's use these numbers:

1. Druid: 45 HP
2. Wild Shapes into Brown Bear: 34 HP, but reduced to 10 Maximum HP (after two kisses).
3. Druid reverts back to normal: 45 HP
4. Wild Shapes back into Brown Bear: 34 HP, or still at 10 HP?

Answer 1

It sticks to the druid and applies in every form.

The other answer you cite argues thusly:

Damage taken in animal form doesn't affect your original form's HP unless you're dropped to 0 HP in animal form and there's excess damage. Nowhere is it suggested that max-HP reduction would work any differently...

This reasoning is wrong. The Wild Shape rule is this:

When you transform, you assume the beast's hit points and Hit Dice. When you revert to your normal form, you return to the number of hit points you had before you transformed. However, if you revert as a result of dropping to 0 hit points, any excess damage carries over to your normal form.

So, when you revert, you return to the number of hit points you had before you transformed--any damage does not "carry over to your normal form" except in the case where the beast form dropped to zero. But the maximum hit point reduction is a separate effect from damage, and Wild Shape doesn't say that effects in general don't carry over between forms.

The target's hit point maximum is reduced by an amount equal to the damage taken. This reduction lasts until the target finishes a long rest.

Who or what is the target? The druid. Therefore the druid's maximum HP will be reduced until the druid finishes a long rest. This applies to every form. When the druid takes on a form, you look up the hit points it will have in that form, and then subtract whatever reduction it's suffering to its maximum HP.

So in this example where the bear loses 24 max HP, in step 3 the druid should be at their new maximum of 21.

Answer 2

The Druid Wild Shapes into a brand new bear form every time

There is no "bear". There is only "the druid magically assum[ing] the shape of the a bear". HP reduction is not carried over, when the druid Wild Shapes back into their normal form the hp pool that had been reduced doesn't exist, and never will again.

Note: interpreting "health points" to include "maximum health points" is kind of questionable.

Answer 3

Reduction of maximum hit points applies to the druid in any form

5e has concepts of "hit points", "hit point maximum", and "Hit Dice". Here is a description of each:

Hit Points

A creature's current hit points (usually just called hit points) can be any number from the creature's hit point maximum down to 0.

Hit Point Maximum

At 1st level, your character has 1 Hit Die, and the die type is determined by your class. You start with hit points equal to the highest roll of that die, as indicated in your class description. (You also add your Constitution modifier, which you’ll determine in step 3.) This is also your hit point maximum.

Hit Dice

Your character’s hit points define how tough your character is in combat and other dangerous situations. Your hit points are determined by your Hit Dice (short for Hit Point Dice).

Wild Shape changes only your hit points and Hit Dice

Wild Shape

When you transform, you assume the beast’s hit points and Hit Dice.

Nothing is stated about your "Hit Point Maximum", so we can safely assume that your maximum hit points are not changed.

Note that modifying your hit die or constitution can result in a change to your maximum hit points. There is no reason to think that changing con or hit die alone would remove Draining Kiss.

Example

A level 2 druid with con 0 transforms into a Cow

• Druid before transformation: Hit die 2d8 (12), con bonus +0, max hp = 12 + 0 * 2 = 12
• Druid after transformation: Hit die 2d10 (11), con bonus +2, max hp adjusts to 11 + 2 * 2 = 15
• Druid is hit by Draining Kiss for 5 damage: max hp adjusts to 15 - 5 = 10
• Druid reverts transformation: hit die back to 2d8 (12), con bonus back to +0, max hp = (12 + 0 * 2) - 5 = 7
• Druid transforms back into a cow: hit die 2d10 (11), con bonus +2, max hp adjusts back to (11 + 2 * 2) - 5 = 10