Does the Aid spell permanently increase HP for Necromancy wizards with the Inured to Undeath feature?

Question

The aid spell increases your current and maximum HP, but only for the duration of the spell.

However, the School of Necromancy wizard's 10th-level Inured to Undeath feature (PHB, p. 119) says:

your hit point maximum can't be reduced.

Does that mean a character with the Inured to Undeath feature can increase their maximum HP permanently by having aid cast on them, since the increase from aid can never fade away even after the spell stops being active?

If this is the case, could repeated applications of aid over multiple engagements ratchet their HP upward each time and increase their HP infinitely?

Answer 1

PHB, p. 205

The effects of different spells add together while the durations of those spells overlap. The effects of the same spell cast multiple times don't combine, however.

Instead, the most potent effect-such as the highest bonus-from those castings applies while their durations overlap. For example, if two clerics cast bless on the same target, that character gains the spell's benefit only once; he or she doesn't get to roll two bonus dice.

RAW does not say that spells cannot stack, but that the effects of the same spells cannot stack.

As such the argument can be made that, since the HP max was never reduced again, the effect of the aid spell never actually disappeared, thus making the character ineligible to be targeted again by the spell, unless it's with a higher spell level; RAW states that the target is affected by the more potent spell effect. Even then, they'd only get the higher max HP bonus, not both.

It might still be a permanent max HP increase, but one that cannot be repeated, so it may not be necessary to counter it.

Answer 2

"Inured to Undeath" is a protective feature, and although not explicitly stated, the implication should be that your Maximum HP cannot be reduced below its normal level. One could also interpret that the loss of Maximum HP from the end of Aid is not a reduction, but a loss of an addition.

In either case, the posited interpretation fails the common sense test. it is highly unlikely the designers intended to produce an infinite HP increase combo. So we must seek the most likely meaning from the written rule.

Answer 3

Does that mean a character with inured to undeath can increase their maximum HP permanently? Yes

Inured to Undeath

Beginning at 10th level, you have resistance to necrotic damage, and your hit point maximum can't be reduced.

RAW, this seems to mean, once you have received a hit point maximum increase rom aid, that increase will stay even after the spell itself has stopped being active.

Could the character then stack multiple aid spells to increase their HP infinitely? No

According to the PHB:

The effects of different spells add together while the durations of those spells overlap. The effects of the same spell cast multiple times don't combine, however.

Note the emphasis on the effects of the spell and not the spell itself. The character is still benefiting from the effects of aid and thus cannot benefit a second time.

Answer 4

Inured to Undeath

Beginning at 10th level, you have resistance to necrotic damage, and your hit point maximum can't be reduced. You have spent so much time dealing with undead and the forces that animate them that you have become inured to some of their worst effects.

While the sentences "resistance to necrotic damage" and "your hit point maximum can't be reduced" are distinct, the whole paragraph can be used to argue that your HP can't be reduced from Necrotic effects only. The second line confirms this by talking about your character being inured to the worst effects that undead have. If you take just the line "your hit point maximum can't be reduced" then even having your Constitution score reduced wouldn't reduce hit points.

And Aid is an abjuration spell so wouldn't fall under not losing HP to necrotic effects.

Thought this was a good answer, but see that really what I am saying is that the GM can rule otherwise, which is actually rule 0 so not saying anything. Though already posted the answer so will leave it.