For better balance; change the upcasting text to

Using a Higher-Level Spell Slot. The damage increases by 1d8 for every two spell slot levels above 4.

Yeah, this spell is totally broken. 

Seriously WotC, how did this get past any sort of testing? You have Spirit Shroud as an excellent example of how this should scale.

Make them expendable. Eg. Spell summons 4 wisps, 4 hits and spell ends. 

Or once per turn. Not per attack.

Awesome spell! It just needs a tweak to the upcasting option, either 1d8 per level or per 2 levels for better game balance. 

They'll probably fix it, and other things. But not till the first print run is sold.

Gee, i wonder why they didn't give this one to Warlocks....

(Morgan Freeman voice)

*He did not, in fact, wonder why they did not give it to warlocks*

Seems fine just monster tatics might need to evolve 

Why do I get the feeling you all read the Spell wrong... Its said any attack ads the dmg. A Magic spell is no attack its a magic action surely you make an Attackrole for a single target but attack is the attack action and not the cast of a spell cause in the new rules the magic action is another point and not once called as attack in this. So i think this spell was just to make normal attacks of caster classes useable...

A magical attack is literally an attack just like any other. There are indeed, four types of attacks. 
1. melee weapon attack, 2. Ranged weapon attack, 3. Spell attack, and 4. Ranged spell attack.  There is no duch thing as a “magic sction” per se, it is called an “attack action” of which there are four kinds. 

Quote from RobertSchaefer >>

A magical attack is literally an attack just like any other. There are indeed, four types of attacks. 
1. melee weapon attack, 2. Ranged weapon attack, 3. Spell attack, and 4. Ranged spell attack.  There is no duch thing as a “magic sction” per se, it is called an “attack action” of which there are four kinds. 

 Strictly speaking, there is now a "Magic Action" in the 2024 ruleset. It is used to cast most (if not all) spells. That said, many damaging spells that involve an attack roll still say "make a melee/ranged spell attack" against the target, which means Conjure Minor Elementals would still proc on those.

It says the creature needs to in the 15 ft as well if I'm not mistaken amd specifies you so how good is it really if you're a squishy caster getting within 15ft of melee range. At least thats how it seems to read for me. That you and the creature you are attacking needs to be in that 15ft radius of the spell.

Why should Wizards be better in melee than every single martial class?

Quote from GwidianofManos >>

It says the creature needs to in the 15 ft as well if I'm not mistaken amd specifies you so how good is it really if you're a squishy caster getting within 15ft of melee range. At least thats how it seems to read for me. That you and the creature you are attacking needs to be in that 15ft radius of the spell.

 Warlock at 10th level hit 3 times with elderich blast as an action then misty step 30ft away. Assuming agonizing blast we are looking at 6d8 (27) + 3d10 (17) + 15 per round and if they got lance of lethargy the poor creature is unlikely to catch up to the warlock meaningfully or escape.

I don't think this will be allowed at my table and my character at that table is a druid. A 10-minute spell that has the potential to do 12d8 per attack? I'll have the wizard doing the same thing. I'll have the whole party multi-classing to get this spell. So, I'm just banning it until they clarify. Honestly it doesn't scale properly even if you limit the scaling to 1d8. It's not like Spirit Guardians at all. Spirit Guardians requires a save can hit once per turn and its very clear what effects still occur if you make the save. This spell is not ready. Many have said it. Treantmonk, D4, Dungeon Dudes, etc. Good rules interpreters and representatives of this community have reviewed, made builds to test it and give solid opinion on why this is not yet ready. It's an interesting idea, but it's not finished. 

Casters have great spells without this. I think I'll leave it out for a hot minute and let Jeremy and the D&D team wiggle their noodles on it and come out with a revision. With all the moving parts to a big D&D update like this, it's ok to see a mistake. I remember much earlier editions having significantly more issues. D&D is great at fixing this kind of thing. Good job team. We all know how to handle this. It's just that we all want to play this build to wreck monsters <evil grin>. Even if they don't fix it, good GMs will handle it. It's simple really. Remove it.

Players will do this kind of thing if you let them, and they won't feel too bad if you don't. That's the life of a D&D player. Your friends will appreciate removing this until it's better reviewed and released.