The archetype is intended to be a give-and-take healer role, supporting already potent druid curative magic with "healing battery" and damage redirection powers. Circle of Dust druids are also capable of assuming a unique form using their wild shape power and leeching off healing done in their presence, giving them synergy with allies capable of healing or in the presence of enemies that can cast healing spells.
Its downsides are it being somewhat "gamey" as far as 5th Edition archetypes go (it makes use of hit dice as a resource to be expended during non-rest situations) as well as potentially interrupting the actions of other players as the druid piggybacks off of events happening during play. It may also be horribly imbalanced, but without a proper playtest in lieu of napkin-math, I can only go with my gut feelings on the numbers.
The Circle of Dust
The Circle of Dust is an order of druids seen as something of an aberration by more traditional druids of the Circles of Land and the Moon. Some are sad, wandering prophets offering succor through sometimes frightening powers coaxed from a ravaged world. The worst of the lot are misbegotten, insane harbingers of apocalypse that preach doom and bring further ruin.
Upon selecting this Circle at 2nd level, the druid gains the ability to siphon life force from healthy and hale allies in order to mend the wounds of others. Both targets must be willing to participate and be within 30 feet of the druid. The druid may act as the source if they so desire.
The source of the healing may donate hit dice up to a maximum of the level of the druid initiating the exchange. The dice are then rolled as though being used to recuperate during a short rest, and the total is given to the target of the exchange. The druid may use this power only thrice before requiring either a short or long rest.
A source that does not possess spendable hit dice (such as a monstrous ally) or one who no longer has hit dice to spend may instead elect to suffer 1d6 points of necrotic damage for each hit die they would have otherwise expended, with the damage total being used to fuel the healing on the target. Any excess is lost.
Theft of Life
Even if the druid of the Circle of Dust does not choose to cast healing magic of their own, their unique abilities allow them to "steal" life energy provided by such spells and use it for their own purposes. Beginning at 2nd level, the druid may use their reaction any time a spell or other magical power that restores lost hit points is used within 60 feet (either by an ally or an enemy). The druid may immediately expend a single hit die and roll it to recover from damage as though they had used it during a short rest.
Naturally, the uses of this power are limited by the number of remaining hit dice the druid possesses.
Ash and Wind
When the druid reaches 6th level, they can expend uses of their wild shape ability to transform into a cloud of dust and cooled embers. The ash and wind form has the following traits:
- You cannot make physical attacks, cast spells, or speak, but you gain resistance to bludgeoning, piercing, and slashing damage from non-magical attacks. You do not lose concentration on spells already cast. Upon reaching 18th level, you can cast spells while in this form (as per the beast spells druid ability).
- When you transform, you assume a hit point total equal to your Wisdom modifier times your level. If all these hit points are lost before you return to your druid form, you drop out of the ash and wind form just as you would with a normal use of wild shape to become an animal.
- You can fly at a speed of 40 feet.
- You can enter any space that is not air tight either through gaps (such as under a door) or cracks (such as in a thin wall). You cannot use this ability to enter magically-sealed locations such as those warded by arcane lock and similar spells, nor can it penetrate any force effect such as a wall of force or globe of invulnerability.
- You have advantage on Stealth checks to avoid notice, as you make very little to no noise.
- You cannot enter water of any volume. Doing so immediately ends the form.
- Natural high winds or the gust of wind spell can push you along easily; you are at disadvantage on Strength checks to resist.
Ash and wind otherwise obeys the rules and restrictions of wild shape in terms of duration, equipment, and actions used to assume or shed the form.
Walking the line between survival and ruin grants a Circle of Dust druid significant resilience against effects that ravage the body. Upon reaching 10th level, the druid has advantage on saving throws against poison and disease and gains resistance to necrotic damage.
Wrack or Repeal
Suffering and destruction are such a part of the Circle of Dust that its most powerful druids can manipulate the echoes of harmful events. Upon achieving 14th level, a druid of the Circle of Dust can wrack or repeal as a reaction any time the druid or an ally within 60 feet suffers from any event that causes hit point damage such as from a physical attack or a fireball spell. The damage suffered is immediately halved and the druid can decide what to do with the remaining half, electing to either wrack or repeal.
If the druid elects to wrack, half of the damage is immediately inflicted back upon the attacker. This damage is of the same type as the triggering attack. For example, if a druid's ally is damaged by a fireball that causes 32 points of damage, using wrack reduces the damage suffered to 16 and inflicts 16 fire damage upon the caster of the fireball. If the caster were resistant to fire, they would suffer half of that damage.
If the druid elects to repeal, half of the damage is converted to healing and can be distributed to any number of allies within 60 feet of the druid, so long as they are not the same individual whose damage was reduced. Using the same above example, the druid could distribute 16 points of healing to any allies that are not the initial target.
The druid may use wrack or repeal once upon reaching 14th level, gaining an additional use at 16th, 18th, and 20th level (for a total of four uses). These uses recharge after a long rest.