Does a Lore Master's Spell Secrets ability change only a spell's damage output, or all references to a damage type?

Question

I have a question about the Lore Master's damage changing feature, Spell Secrets. It says (empashis mine):

When you cast a spell with a spell slot and the spell deals acid, cold, fire, force, lightning, necrotic, radiant, or thunder damage, you can substitute that damage type with one other type from that list (you can change only one damage type per casting of a spell). You replace one energy type for another by altering the spell’s formula as you cast it.

Would this changing of the type of damage affect every instance of the damage type, or just the damage type of actual damage done? For example, vampiric touch has two instances of “necrotic damage”, but only one is doing damage:

Make a melee spell attack against a creature within your reach. On a hit, the target takes 3d6 necrotic damage, and you regain hit points equal to half the amount of necrotic damage dealt. Until the spell ends, you can make the attack again on each of your turns as an action.

Does using Spell Secrets to change the damage done by vampiric touch also change the part of the spell that doesn't do damage, but refers to how much necrotic damage you dealt? Basically, would vampiric touch still heal the caster if it dealt fire damage?

Answer 1

What an interesting question.

Under RAW, it would not heal. Spell Secrets is pretty specific that only the damage type is substituted, and furthermore, at least for the wording under Vampiric Touch the healing specifically comes from necrotic damage dealt.

Make a melee spell attack against a creature within your reach. On a hit, the target takes 3d6 necrotic damage, and you regain hit points equal to half the amount of necrotic damage dealt. Until the spell ends, you can make the attack again on each of your turns as an action.

Technically there was no necrotic damage dealt here. And that makes sense. Why would fire damage heal the caster like siphoned off necrotic energies.

That said, RAI, it would not be the end of the world to extend the healing to this power.

NOTE: Unearthed Arcana is playtesting material, and may not be balanced, worded well, or workable.

Answer 2

There is no good reason to believe it wouldn't. It can change only one damage type, but it does not say it only changes one reference to that one damage type.

In the case of Vampiric Touch, the damage changes from necrotic and the healing is based on the (changed from necrotic) damage dealt.

The clear intention of the restriction on that ability is for spells like Ice Storm and Prismatic Spray, that deal multiple types of damage in one casting. The first deals ice and bludgeoning - only the ice can be changed, and only to another element, while the bludgeoning damage is unaffected. The second deals a variety of "elemental" damage types, only one of them can be changed.