Is this "Circle of Shadows" Druid Circle balanced compared to Circle of the Moon

Question

I came up with my own subclass. I modeled it slightly after the Circle of the Moon, which is why I'm specifically asking for comparison to it. Well, here it is.

Druid Circle: Circle of Shadows

Once there was a dark elf, he had had his heart set on joining a druid circle. All of those circles shunned him. He started his own circle. The circle of shadows.

Shaded Form

“The shadow didn’t consume me; I consumed the shadow.”

Starting at 2nd level, when you use wild shape, you can transform into a Shadow. You also learn the Umbraturgy cantrip (from Dark Arts Players Compaion, which is homebrew). Finally, you gain darkvision for 60ft, if you already had it, it increases by 60ft.

Shadow Enhanced Strikes

“The shadow moves with me; we are becoming one.”

Starting at 6th level, your attacks in regular form and beast from are considered magical for the purpose of overcoming resistance and immunity, in addition, you can spend a spell slot and enhance a weapon. The weapon you enhanced does an extra 1d4 necrotic damage on a hit per level of expanded spell slot. You lose the effect if you leave the darkness or dimness.

Improved Shadow Form

“The shadow climbs into my soul, second by second it reaches more.”

At 14th level, when you use wild shape, you can transom into a wraith. You gain the benefits of shadow enhanced strikes while in this form.

A True Wraith

“I join hands with my shadow we sing songs of praise to the darkness that is inside me. and the darkness the he is made of. I am one with the shadow.”

At 14th level, you now can expand a spell slot to gain a hovering speed but can hover no more than 5ft off the ground. The hovering speed equals the level of the spell slot spend times 10 (1st level = 10ft 2nd level = 20ft etc.) In addition, you can cast the invisibility spell (lowest level) at will, but you must be in dim light or darkness.

Umbraturgy

Transmutation cantrip
Casting time: 1 action
Range:Touch
Combontents: V
Duration: Concentration, up to 1 hour

You compell shadows to create one of the following effects at a point you can see within range:

• The shadow of a creature or object changes size or shape, up to a maximum of double or half its normal size.

• You cause shadows to conceal a creature in dim light or darkness, giving them advantage on their next Dexterity (Stealth) check within the next minute as long as they remain in the dim light or darkness.

• A creature or object's shape becomes either harder or softer, making its form either easier or harder to to discern from the shape of the shadow.

If you cast this spell multiple times, you can have no more than two of its non-instantaneous effects active at a time, and you can dismiss such an effect as an action.

Answer 1

Two or three concerns with "balance" and concept

Up front, if you look at the description of the druid in the PHB, the antipathy for the undead is spelled out clearly. Deliberately turning into a Shadow or Wraith seems inconsistent with the class as written.

Druids accept that which is cruel in nature, and they hate that which is unnatural, including abberations(such as beholders and mind flayers) and undead (such as zombies and vampires) (PHB p, 65)

However, a variety of trope breaking sub-classes have arisen (Paladin of Conquest, Celestial Warlock) since the PHB was issued. If your table is good with a druid going to the dark side, it's not a big deal.

Team internal conflict potential:

If your party has a cleric, and your druid is in Wraith or in Shadow form, and the cleric turns undead by using Channel Divinity, your undead form Druid may have to flee the battle. This could cause some tactical problems, or, it might require that you delay any change into a Shadow or a Wraith until after the cleric has caused the enemy undead to flee. (You do get to roll a save versus the cleric's spell DC). This could be hilarious now and again, and it could also send your PC off into a corner until a fight is over. Or destroy your PC!

In Shadow form, if the Cleric Turns Undead and is over level 5, the druid in shadow form is .. destroyed. (Channel Divinity, Destroy Undead, Table, Basic Rules). At least in Wraith form it can't be destroyed. (Upper Limit to destroy is CR 4).

Healing spells: the druid needs to be out of the undead form to receive healing spell benefits from party members.

The features

1. At will invisibility at level 14

   In addition, you can cast the invisibility spell (lowest level) at will, but you must be in dim light or darkness.

   And once cast, the druid is invisible. That replicates the effects of a legendary item, ring of invisibility. Wizards do not get this until level 18 (with a level 2 spell that is cast at will). Per your comment under the question, limiting this to "while in shadow/darkness/dim light" would be a good move. (And thematically a very nice fit).

2. The Wraith at level 10

   you can transom into a wraith. You gain the benefits of shadow enhanced strikes while in this form.

   Conceptually, this is most excellent. Wraiths have a lot of damage reduction potential, but also the ability to raise spectres which turns this (potentially) into something more than a simple change of shape. I'd consider limiting the specter raising ability, or removing it. Let's compare with the Earth Elemental form option of a straight up Moon Druid at level 10. Consider that it costs two uses of Wild Shape to become an elemental: you may want to limit the Wraith similarly.

   Earth elemental can earth glide, Wraith can move through solid objects. Wraith is faster when flying. That's a wash.

   Wraith has lower AC (13/17) and half of the HP (63/127) of an Earth Elemental.
   EE Damage Vulnerabilities: thunder
   Wraith Vunlerabilities: none.
   EE Resistances: bludgeoning, piercing, and slashing from nonmagical attacks
   Wraith Resistances: acid, cold, fire, lightning, thunder; bludgeoning, piercing, and slashing from nonmagical attacks that aren’t silvered (Advantage to Wraith)
   EE Damage Immunities: poison
   Wraith Immunities: poison, necrotic.
   EE Condition Immunities: exhaustion, paralyzed, petrified, poisoned, unconscious
   Wratih Condition Immunities: charmed, exhaustion, grappled, paralyzed, petrified, poisoned, prone, restrained

   Languages and senses: a wash.

   EE does more damage, and double damage to structures.
   Wraith can enter a wall/structure, and for the cost of a few HP per round, be un-attackable until the object is destroyed. At higher levels, where more damage is often done per round and dragon breath is a significant damage dealer, this can be used tactically to limit damage.
   Call it a wash.

   Life Drain.

   With the big bags of hit points that are monsters at and above CR 10, this won't be that big of a deal. But it will kill some enemies outright near the end of a fight.

   Create Specter.

   Here, a caster (druid) with a full spell progression also can create a small band of summons (7) without spending a spell slot. 7 CR 1 creatures with significant damage resistances and condition immunities who also have life drain, can fly, and have incorporeal movement. Against some high CR enemies that won't matter, against others this swarm will be a significant change to the action economy.

   The wraith targets a humanoid within 10 feet of it that has been dead for no longer than 1 minute and died violently. The target’s spirit rises as a specter in the space of its corpse or in the nearest unoccupied space. The specter is under the wraith’s control. The wraith can have no more than seven specters under its control at one time.

   For how long does the druid / wraith wander about with its little posse of spectres? Granted, at this high of a level, humanoids may not be your most common foe, but this druid could drop by a village, make half a dozen specters, and wander off with a little undead posse. No significant resource cost.

   Reccomendation: either a revision to this power, or, just remove it such that the "form" is retained but this special ability to create a band of specters doesn't come with the transition. Added benefit of removing it: thematically appropriate, given the PHB descriptive text at the beginning of this answer.

3. Speed (hovering/flying) of 70 at level 14; 90 at level 17

   The hovering speed equals the level of the spell slot spend times 10 (1st level = 10ft 2nd level = 20ft etc.)

   Why not? At that level you are up against some pretty tough opponents, so this should not skew combat too far out of whack.

   Since a wraith already has a flying speed of 60, are you proposing to add more speed on top of that, or give a flying speed to the druid's normal form? I'd suggest limiting this to only when in druid form, and when changed into wraith form simply use the 60' flying speed.

   Or, play test this in wraith form with some high level encounters and see how much of an advantage speed offers. A speed of 130 at level 14 looks to be skewed, but it does cost a resource. Since you have to expend a spell slot for this speed, you need to clearly define the duration of the speed boost if you want this to be additive. Consider spells like fly for duration ideas.

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Umbraturgy: not sure of its mechanics, the concept is a good one

Balance wise, the concentration looks to be too long
This one's a matter of taste, but having these effects go on for an hour, multiples, looks to be stronger than most cantrips, particularly as the granting of advantage is rolled into this. (Conceptually, I love the idea behind this cantrip)