combo of grim harvest and a number of other spells

[Rentirith]

Hey there Giantitp-ers. I had this question that I posed over in the dnd reddit and though I got a handful of answers, I didn't receive an answer that answered my question; that being this: If I had access to the grim harvest feature, what types of other, non-wizard (specifically warlock) spells could qualify to trigger this health gain?

My main spell in question is Hex. This 1st level bonus action fan-favorite lets you deal an extra 1d6 necrotic damage to creatures that you hit with an attack roll and has the potential to scale up to 5th level with warlock spell-scaling. the grim harvest feature says that "At 2nd level, you gain the ability to reap life energy from creatures you kill with your spells. Once per turn when you kill one or more creatures with a spell of 1st level or higher, you regain hit points equal to twice the spell's level, or three times its level if the spell belongs to the School of Necromancy. You don't gain this benefit for killing constructs or undead." Does this mean that killing something under the effects of hex would extend the healing to you, even if you use a cantrip to kill the creature?

My arguments for the answer being no is that the spell used is what is important, and technically the hex is just a rider effect on the spell or whatever that you actually use. Eldritch blast is a cantrip, ergo you didn't use a spell of 1st level or higher.

My arguments for the answer being yes is that you still spent a spell slot of 1st level or higher in order to kill the creature and that creature took damage from that same spell. Vampiric touch one of the most iconic uses for this wizard feature since it is concentration, so you are casting the spell once, concentrating on it, and using subsequent turns to attack a creature with it. Also, because of the way that combat works (and this next part might just be my perception of the way the game works) all actions and effects happen simultaneously, so it isn't like an eldritch blast hitting a creature does force damage first then does necrotic damage; all of the damage happens at the same time, and thus cannot be picked apart to see if the necrotic damage is what kills the target instead of the cantrip's force damage.

This then opens up other arguments for some other warlock spells like armor of agathys. You cast the spell, it isn't concentration, but the spell specifically deals damage to others who hit you, so if this damage kills an enemy then that would trigger the harvest, right?

If anyone has a good, logical answer to this question, or has experience with this situation, I would appreciate some feedback on the matter. Thanks guys!

[Nettlekid]

Hex is weird. I think the fairest way to rule it, even though this adds an extra level of confusion, is that if the extra d6 of damage that you dealt with your attack is what lands the killing strike against the target (so if you dealt 1d10+1d6 damage, got a 7 on the d10 and a 4 on the d6 and the target had 9 HP left) then Hex is what killed the target and so Grim Harvest triggers.

[Requilac]

As a DM, I would personally handle it so that the if the effect of a spell is what killed the creature then you would get the extra HP even if you didn't necessarily cast the spell on that turn. So if you hit a hexed target with eldritch blast, then if the damage from the cantrip itself was enough to kill the creature than you would get no extra HP but if the damage from the rider after the cantrip damage is what killed the creature you would gain the HP. Armor of agathys would thusly grant the HP regain to. Keep in mind though that this is just what I would do if I were DMing and I cannot back this up with any sort of evidence.

Also keep in mind that I am incredibly lenient when it comes to D&D rulings and will sometimes even let my players use RAF to override RAW, so I might not be the best authority on this matter.

[Keeg]

I have been googling the exact same question and have yet to find a good answer. I am building a necromancer and thinking dipping 1 in warlock for Hex would be killer for this combo.

Thoughts: I wouldn't dissect the attack like Nettlekid.

if the extra d6 of damage that you dealt with your attack is what lands the killing strike against the target (so if you dealt 1d10+1d6 damage, got a 7 on the d10 and a 4 on the d6 and the target had 9 HP left) then Hex is what killed the target and so Grim Harvest triggers.

I think the confusion would just make the DM's life harder. The target gets dealt the d6 of necrotic damage even if it goes passed 0 HP with the force damage. Let the Necrolock get the 3 HP from grim harvest (1st level spell x3). It's 3HP and a cool effect.

Same with reaction damage / armors. If it's a spell it is acting on the enemies turn so it's a new turn.
Once per turn when you kill one or more creatures with a spell of 1st level or higher, you regain hit points equal to twice the spell’s level

Let your Necrolock control life energy on the field. Is your party cool with you absorbing the life energy of every baddie y'all come across? Story line just gets better allowing it to proc.

[Wildarm]

Taking the example of Hex and a cantrip. You could upcast Hex to 5th level making it last all day. Then whenever you kill anything with Cantrip+Hex you gain 15HP. That is ALOT of sustained healing with only a single spell slot expended(and your concentration). 15HP for a 10th level wizard/warlock is something like 30% of their max HP.

I'm pretty conservative in rulings on the side of balance. As others have mentioned, I would allow them to gain that bonus heal only when the extra d6 is enough to kill the creature. If they are using EB+Hex then that will still occur pretty often due to the multiple beams and hex stacking.