Am I reading this wrong?

A target takes 8d6 necrotic damage on a failed save, or half as much damage on a successful one.

Which means, of all affected in the circle, the caster only chooses 1 that will be damaged? "A Target" implying single target only, and not all in the AOE

Not quite.

Each creature in that area must make a Constitution saving throw. A target takes 8d6 necrotic damage on a failed save, or half as much damage on a successful one.

Everyone in the circle is a target within the AOE. Target does not imply a single target unless it says A single target.

Quote from Chalm >>

The HUGE AoE of this spell makes it fantastic for boss fights!

 Since it doesn't do too much damage, it's not ideal for fights against a lone, powerful creature.  Buts its massive AoE makes it an amazing choice for hordes or armies.  So this would be useful against the boss's minions, but it wouldn't be very powerful against the boss itself.  

You do get around evasion mechanics though, only a handful of creatures can take no damage of successful con save

Quote from tyranttoxicroak >>

Con is not a better save than Dex, its very similar in most cases, but sometimes even worse because by the time you can cast this spell, you'll be very hard-pressed to find a monster with a Con below 16. The radius is nice and it does seem to extend through cover, but freezing sphere has the same radius, 10d6 cold (necrotic is lauded as being a really good damage type, and while devils and demons aren't resistant to it like they are cold damage, elemental adept exists and a lot of undead are resistant or straight immune to necrotic) and can restrain creatures in water. This spell is cool but it needs to do at least 10d6 and maybe have a secondary effect.

 It’s good for a boss to use when the party has rogues and monks.

Quote from Ryuma >>

Nice spell but unless you are first in the initiative order your going to have to figure out how NOT to include your party members in the AoE as your tanks rush up to meet the baddies. Its a necromancy spell so an evocation wizard can't sculpt pockets of safety. Maybe a Sorcerer with careful metagagic?

 How about you ASK them to hang back for a second, it's the nature of a caster to be background sometimes and other times completely steal the show. It's not like non casters can do AoE, especially large scale. Or you initiate combat with this, it has 150 ft range (210 radius included), DnD might trend toward close range fights, but you can take on entire hordes with this, or kill the entire crew of a pursuing naval ship, or more if they're close enough together.

Quote from tyranttoxicroak >>

Con is not a better save than Dex[...]

 It's not affected by evasion though.

I just noticed one overlooked aspect of this spell.  The spell's damage scales by TWO dice, instead of one, unlike fireball.  

60' Radius instead of a 20' radius.  Also, there is a lot more resistance to fire damage than necrotic out there.

Quote from HailRobonia >>

the problem is the material component cost 

 The bigger problem is the AOE is highly situational.  Depending on the campaign, you might not get into a situation where you will need a spell with an AOE larger than fireball.  A high AOE makes it harder to avoid friendly fire, and since this is necromancy and not evocation, you can't sculpt it.  The usefulness of this spell will depend on your campaign.  In cramped dungeones, its obsolete, as you might be able to get the job done with a synaptic static.     

Quote from brovick >>

WHY would you choose this over fireball 

 

 just in case you put the character in with a bunch of low levels and are fighting low-level enemies and want to mess with your DM

Quote from Ech0_2G >>

Because Fireball is OP and constantly using it is boring.

 Fireball was purposefully made to be exceptionally powerful for it's level, just because it's so iconic.  

This spell sounds nice on paper, but I'm having trouble seeing any reason why anyone would ever take it?

- For one, Circle of Death is just straight up inferior to Fireball at the 6th, 7th, and 8th levels. Circle of Death does less damage, it's based on a saving throw that creatures have an easier time succeeding against, you must expend a spell slot of 6th level or higher to cast it, and the material components—while not the end of the world in terms of cost—will probably require an action for you to fetch it out of your backpack or similar storage unit and an additional free hand since your arcane focus doesn't work here. The two things Circle of Death has going for it compared to Fireball are its superior damage type, which is a fairly small benefit all things considered, and its larger area, which isn't strictly a good thing.

- Even if you really do want the large area, and there are instances where you will want it because Fireball ain't going to cut it, why would anyone take Circle of Death when they could take Freezing Sphere instead?. It deals more or equal damage at 6th, 7th, and 8th level, has better range, has only a slightly worse damage type, and has more utility thanks to its water freezing effect. Looking at Circle of Death and comparing it to other spells, it just doesn't do enough.

- Once you do gain access to 9th level spell slots, Circle of Death becomes somewhat appealing because it ties Fireball's damage and surpasses Freezing Sphere's damage at 9th level, but I would argue that you realistically shouldn't be casting any of these spells as a 9th level spell. Even if you limit yourself to casting spells for damage purposes, significantly better options begin to show up when you reach this level, and it's not even close. I advise that you check out both Meteor Swarm's unbelievably high damage with incredible range as well as Psychic Scream's utility heavy AOE that's larger and calls for Intelligence saving throws.

While Circle of death's scaling sounds nice in theory, it's outclassed by other spells at any level you might otherwise want to cast it at. This spell just doesn't do enough. It's not even all that great if you want to be a flavor-heavy necromancer, shadow Sorcerer, or other type of dark caster of your party. Spells like Chill Touch, Finger of Death, Negative Energy Flood, Toll the Dead, and Vampiric Touch come decked with additional effects that can make the spells you cast a bit more likely, whereas Circle of Death is just "a sphere of negative energy" that comes and goes in one turn and pretty much nothing else beyond that.

Why isn't this available to the Death Domain Cleric? 💀☠️

Domain spells only go up to 5th level, whereas this spell is 6th. I agree that it makes sense, but it should probably just be added to the cleric spell list as a whole rather than breaching the rules to give one subclass one new spell.

Ah, yes, good point! 😅👍🏼

Notice that this spell’s area is unaffected by cover.

It's a con save rather than a dex save. In some corner cases when you now what you are fighting has shit con but good dex it can be useful

Also point of order, it doesn't say that total cover stops the damage

I could have sworn that creatures that die to this spell are raised as zombies.