Inured To Undeath (bolding mine):
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.
How does this feature interact with items that temporarily or conditionally improve your maximum HP, either through increasing the character's CON score or by directly influencing maximum HP?
A similar question was posed with regards to the Aid spell, which had some interesting discussion.
But I'm specifically curious on how the feature interacts with Amulet of Health, Belt of Dwarvenkind, and other features that modify the CON score of the user.
Amulet of Health:
Your Constitution score is 19 while you wear this amulet. It has no effect on you if your Constitution score is already 19 or higher without it.
If a lvl 10 Necromancer with a CON modifier of 2 attuned to the Amulet of Health, then later in their adventuring career unattuned to the item, would their maximum HP stay at the level of the Amulet or return to its unaltered state?