[RPG] Do damage resistance and temp hit points from False Life and the Heavy Armor Master feat stack

dnd-5efeatsspellstemporary-hit-points

I have a multiclassed cleric/warlock with both the Heavy Armor Master feat and the Eldritch Invocation; Fiendish Vigor (which allows me to cast False Life at-will).

The Heavy Armor Master feat (PHB pg. 167) states;

While you are wearing heavy armor, bludgeoning, piercing, and slashing damage that you take from non magical weapons is reduced by 3.

and False life (PHB pg. 239) states;

Bolstering yourself with a necromantic facsimile of life, you gain 1d4 + 4 temporary hit points for the duration.

I'm curious as to whether or not this stacks I.E if I take 5 slashing damage, is that reduced to 2 because of Heavy Armor Master and then the temporary hit points I gain from False Life absorb the rest?

Best Answer

Yes, false life and Heavy Armor Master work together.

Temporary HPs function exactly as normal HPs, except that they are designed to be lost first, before applying residual damage (if any) to your normal hit points. They are not to be mistaken for damage resistance, which is the ability to halve the damage taken in some situations, or damage reduction, which is the ability to reduce the damage taken by a fixed amount. All of them, however, should stack.

Player's Handbook (p.198)

When you have temporary hit points and take damage, the temporary hit points are lost first, and any leftover damage carries over to your normal hit points. For example, if you have 5 temporary hit points and take 7 damage, you lose the temporary hit points and then take 2 damage.

If you possess some form of damage reduction, like the Heavy Armor Master feat, or some form of damage resistance, like the rage ability, you apply these effects first, just like you would when receiving damage normally (remember that, as per the rules found on p.197 of the PHB, damage resistance is the last modifier to be applied to damage taken). In effect, temporary HPs are a way to magically augment your ability to take punishment.

Contrast this situation with an abjurer's Arcane Ward. In this ability's description, the ward is described as a separate construct having it's own set of HPs, rather than giving you temporary HPs. As such, one could possess both an Arcane Ward AND temporary HPs (although temporary HPs from different sources still wouldn't stack), but the ward shouldn't, at least according to RAW, benefit from damage reduction or resistance effects. Indeed, it is not you taking the damage, at least until the ward breaks.