The Hexblade gives some pretty awesome boons to a Warlock looking to get down and dirty alongside their tankier brotheren, but the curse they give to their enemies can be used from any range, not just melee.

In a recent game my DM and i came across a unique scenario (or at least I haven't found anyting online to answer the question) where my character, a hexblade warlock/sorcerer, used magic missile on the boss who was under the hexblade curse. Now according to the hexblade in UA,

"You gain a bonus to damage rolls against the cursed target. The bonus equals your proficiency bonus."

Which is nice, but it means damage rolls. Not attacks. And if we look at magic missile,

"A dart deals 1d4 + 1 force damage to its target. The darts all strike simultaneously, and you can direct them to hit one creature or several."

A dart. The question that came up was does this mean a hexblade can add their prof bonus to each dart as they're, by the reading, each a seperate damage roll? My DM said yes, but I'm curious about others opinions, especially since Hexblade is coming out in Xanather's and may still have that wording.

Ah, almost forgot.

The Hex spell goes

"You place a curse on a creature that you can see within range. Until the spell ends, you deal an extra 1d6 necrotic damage to the target whenever you hit it with an attack."

Which directly mentions attack rolls, not damage. Hence the idea that magic missile, while it couldn't benefit from Hex, could benefit from the Hexblade Curse ability.

RAW Hexblade curse would trigger because it looks for damage rolls and Magic Missile uses 1d4+1 damage roll. 
RAW Hex would trigger because Magic Missile uses a attack, even if it doesn't use a attack roll.

I do not know if Hexblade's curse requires concentration but I think Hex does and that may be a limiting factor. If not you are looking at 

1d4+1+x+1d6 where x is your proficiency bonus. I am not 100% sure you would get the Hex damage for each roll as I cannot remember if each dart counts as a individual attack (I think it does but like I said not 100% sure). 

Saddly the curse can only target one creature at a time, and until 14 you can only use it once a short rest.

That link does answer my question though. Thank you!

Welp always good to learn something new. I pulled up the spell when I got home (I should stop answering these on my phone and metered data) and ya MM does not have the word attack anywhere so it wouldn't trigger Hex, thank you for the correction Sillvva.

Magic MIssile doesn't have one damage roll per dart; it's one damage roll, period. Each dart does the same amount of damage.

This is because of the rules of Damage Rolls:

If a spell or other effect deals damage to more than one target at the same time, roll the damage once for all of them. For example, when a wizard casts fireball or a cleric casts flame strike, the spell's damage is rolled once for all creatures caught in the blast.

So anything that grants a bonus to damage rolls specifically grants a bonus to each dart. Note that this is different from features like Fury of the Small, which affect the final damage a creature takes, not each dart: "When you damage a creature ... you can cause the attack or spell to deal extra damage to the creature." There's already precedent for this with wizard's Empowered Evocation. See these tweets:

@JeremyECrawford: "@BrailSays: Empowered Evocation does benefit magic missile's damage roll."

@BrailSays: "@JeremyECrawford +x per bolt,even on same target?"

@JeremyECrawford: "@BrailSays Yep. It's one damage roll, just like fireball, but that roll can damage the same target more than once."

And

@BrailSays: "@JeremyECrawford @_Matafer So Scorching Ray gets +X 1 time per cast,but Magic Missile gets +X on every bolt?"

@JeremyECrawford: "@BrailSays Correct. Magic missile is an oddball, in that it functions a bit like an area-damage spell ("strike simultaneously"). @_Matafer"

The interaction between the Hexblade's Curse and Magic Missile is a bit funky since Magic Missile could simultaneously target the cursed target and other targets. The most sane ruling is probably to say each dart that hits the cursed damage deals 1d4 + 1 + Proficiency Bonus and each dart that doesn't deals 1d4 + 1.

Quote from Sillvva >>

The question is. Would it be exactly the same as Fireball + Elemental Affinity which does 8d6+ABI? So would it be 3d4+3+Prof (since you roll the damage once, not separately for each bolt) or 3x(1d4+1+Prof).

Late to the party, but I confirmed this one myself, with Mr Crawford. Magic Missile DOES work with Hexblade's Curse, exactly the same as it does that Evocation wizard feature. So at level 17, magic missile would be hitting a Cursed target for 1d4+7 per missile.

 Very late to the party...Is this the correct interpretation:

Quote from Terakhan >>

Late to the party, but I confirmed this one myself, with Mr Crawford. Magic Missile DOES work with Hexblade's Curse, exactly the same as it does that Evocation wizard feature. So at level 17, magic missile would be hitting a Cursed target for 1d4+7 per missile.

As far as I know, yes. All it takes is a magic initiate with sorcerer or even just a single level in it to really deal that single target damage once a short rest.

Now the Question is WHY?...

WHy would you Use Magic Missile when as a Warlock you have Eldritch Blast who's far superior?...

I mean at lvl 18 with 19-20 in CHA you get PER EB X4 1D10+D6+8 dmg and its a CANTRIP...

For when missing isn't an option. 1d4+7 x 3 as a first level spell that doesn't need an attack roll is huge. That's a minimum of 8 damage a missile, or 24 total at just a first level. Warlocks auto cast at 5th, so suddenly that's four extra darts for 70 damage minimum unavoidable save for a shield spell.

Compared to that EB who's minimum would only be 40 and that's if you hit (curious as to why it's plus 8 to the damage though.)

If we changed it to hexblade curse that would be 1d10+1d6+5 (agonizing) +6 (hexblade curse) for way more damage. But that has a chance of missing.

Was under the impression that it had a saving throw, so yeah it as more precision.

Still its a Once or Twice kind of thing, while EB you can use it ad nauseum, wich for me is better, since i hate the Vancian magic systeme, never understood why they reverted back to it after the good idea that was encounters/dailies powers in 4th..., but thats another issue.

Also EB is far more customizable with the right Invocations.

Jeremy Crawford answered the question exactly about hex + magic missile. HERE (Basically, No "to hit" roll, means it does not trigger hex)

He clarified magic missile is one damage role that you apply to all the darts. HERE

He also clarified Hexblades cures. HERE Basically saying IT DOES NOT need an attack role, it is only the damage role as long as its the cursed target. 

He also clarified Empowered evocation can effect it as a single role. HERE which is a similar effect.

So the point being ... yes if you were to have a Evocation Wizard (Evoker lvl 16), Hexblade Patron Warlock lvl 1, Sorcerer level 3 meta magic empowered spell, Roll 1d4 +1, re-roll if it is low to double your chance of getting a 4 (on a 1/4 chance), add +6 for Hexblades curse, add +5 for intelligence modifier, to get 16 damage x each missile, using a 9th level spell slot for 11 darts or 176  force damage with not hit or resist... HOWEVER your basically a wizard that gave up spell mastery, signature spell, your level 19 ASI/Feat and your 9th level wizard spells for it (wish, meteor swarm - 140 fire/blug dam. dex save for half, power word kill 100 damage or less instant kill with no save or if they have 101 does nothing, etc). On top of that if you roll a 1 twice even with this setup your damage drops to 143 and your average is 159.5 but for a significant buy it. The errata says its per role and Jeremy Crawford said Magic missile is one damage role as above then scorching ray is nerfed but NOT magic missile. So as it stands this still works.

If your just doing Warlock with Hexblades Curse your only going to have level 5 spell (7 bolts) slots at +6 for an average of 66.5 which is not broken and can only cast it 4 times per battle (without a Rod of a pact keeper, then its 5). But how are you getting magic missile to begin with? 

I think the best use is Sorcerer 17, Hexblade 3 so you have 9th level spells at +6 with two chances at rolling a 4 (using empowered spell meta magic) for an average of 104.5 but you get two attempts for a higher 121 damage with a 4. However what else are you using the empowered spell meta magic on? If nothing... well it comes with a cost. (Since your player is a Hexblade / Sorcerer, its really going to reduce the power of this combination for every level in hex blade after the first 3 because it will be reducing the max spell slot level he can cast it at and then number of spell slots he has to use it with.)

Hexblades curse not hex, you are confused