I've spent a good amount of time creating this druid subclass but am having trouble finding people to help playtest and look at it, so I thought I would post it here. Please leave some comments on whether you think the subclass is over tuned or under tuned and, if you could, I would really appreciate a playtest from some fellow DND enthusiasts. Feel free to comment on anything -- from the wording to the mechanics themselves -- and please tell me if you think this is a good proof-of-concept. For context, the Circle of the Aurorae (aw-ROAR-ay) is a battlefield control druid who uses persistent magical conduits to promote fast repositioning and melee damage rather than spellcasting. The subclass is based on the natural phenomenon aurora borealis. Happy reading! 

Druid – Circle of the Aurorae

Druids of the Circle of the Aurorae seek to draw power from Nature's raw breath, which manifests in the sub-cosmic rays of light which mortals term aurorae. Their order grants them the strength to summon and stride through these radiant currents, blessing allies with their beauty while dazzling those who threaten the natural world. These druids see aurorae as more than a spectacle; rather, they represent the living pulse of the world, flowing unseen through the heavens before briefly revealing themselves as dancing curtains of emerald, violet, crimson, and radiant gold. By learning to guide these celestial currents, Druids of this Circle weave luminescent pathways on the battlefield which confound those who seek to bring down the natural order. 

Coronal Conduit (Level 3)

As a Bonus Action, you can expend one use of your Wild Shape to create a Coronal Conduit, a cascading flow of auroral energy. The conduit is a 20-foot-long, 10-foot-diameter horizontal cylinder that originates from you or from either end of one of your existing Coronal Conduits, and it extends in a direction you choose. Coronal Conduits can't overlap.

The conduit remains fixed in place for up to 1 minute. Maintaining it requires Concentration, as if concentrating on a spell. All Coronal Conduits you create share the same instance of Concentration.

The conduit sheds Bright Light for 10 feet and Dim Light for an additional 10 feet. Creatures can move through a Coronal Conduit freely. Entering or leaving a conduit has no effect unless one of your Circle of the Aurorae features says otherwise.

When the conduit appears, each creature of your choice in it must make a Constitution saving throw against your Spell Save DC. On a failed save, the creature takes 1d4 Radiant damage, is lifted 10 feet into the air, and remains suspended there. While suspended in this way, its Speed is reduced to 0, and it has disadvantage on attack rolls as the dazzling currents of the aurora obscure its vision and impede its movement. At the end of each of its turns, the creature can repeat the saving throw, using Strength instead of Constitution. On a success, the effect ends, and the creature falls unless it can remain aloft by other means.

While you are in a Coronal Conduit, your Speed is doubled.

Circle of the Aurorae Spells (Level 3)

When you reach a Druid level specified in the Circle of the Aurorae Spells table, you thereafter always have the listed spells prepared.

Boreal Surge (Level 6)

Often, those who provoke the tides of an auroral flow find themselves burned by the currents they disturb. 

While you are in a Coronal Conduit, you may add your Wisdom modifier to Constitution saving throws you make to maintain Concentration on your Coronal Conduits.

In addition, when a creature makes an Opportunity Attack against you while you are in a Coronal Conduit, you can use your Reaction to regain hit points equal to 1d4 + your Wisdom modifier, and the attacker takes 2d8 Radiant damage.

Immediately after you use this Reaction, the Coronal Conduit you are in ends, and you regain one expended use of your Wild Shape.

Empyrean Torrent (Level 10)

By embracing the auroral flow, you move as effortlessly as light itself. 

When you create a Coronal Conduit using Wild Shape, you can create two Coronal Conduits instead of one. Each conduit must originate from you or from either end of one of your existing Coronal Conduits.

While you are in a Coronal Conduit, you have a flying Speed equal to twice your walking Speed.

After moving at least 20 feet through a Coronal Conduit on your turn, choose Cold, Lightning, or Radiant damage. You have resistance to the chosen damage type until the start of your next turn.

Once on each of your turns, after moving through two or more different Coronal Conduits, you can use a Bonus Action to empower your next attack before the end of the turn. If that attack hits, it deals an extra 1d8 Radiant damage for each different Coronal Conduit you moved through this turn, to a maximum number of d8s equal to half your Druid level (rounded up).

Incandescent Weave (Level 14)

Though few druids ever master more than a single current, the eldest of the Circle weave entire skies of living light, gliding through the Material Plane with effortless grace. 

When you create a Coronal Conduit using Wild Shape, you can create three Coronal Conduits instead of one. Each conduit must originate from you or from either end of one of your existing Coronal Conduits.

Your Coronal Conduits can pass through nonmagical objects and terrain. While you are in a Coronal Conduit, you can move through nonmagical objects and terrain as though they were difficult terrain as your body becomes a thread of auroral light carried within the current. If you end your movement inside an object, you are immediately moved to the nearest unoccupied space and take Force damage equal to twice your Druid level. You can't use this movement to pass through objects thicker than 5 feet.

In addition, while you are in a Coronal Conduit, the first time you fail a Constitution saving throw to maintain Concentration each round, you can choose to succeed instead.

This is pretty solid, but I do have a couple of notes.

1: Concentration already ends when you're Incapacitated or choose to drop it, so that bit is rather redundant.

2: Steel Wind Strike seems like an odd spell choice. The others are great, though. This one's just out of place.

3: The capstone isn't very interesting at all. I have no idea what it could be, but something that's more than just a buff would be nice.

4: The mechanics are very interesting, but I'm not getting all that much of the aurora theming. This is definitely better than going full ham on Blinding and Radiant damage, but I don't think all of the mechanics entirely fit the idea. I do like the Conduit thing though. That is cool.

Thanks for the feedback! I'll keep it brief, but these are my counter-thoughts/original intentions.

1. I am fairly new to the game, so this is extremely helpful, thank you!

2. I was trying to find a spell that synergized with movement and/or a solid melee choice and settled on steel wind strike, even though it doesn't really have much to do with the whole aurora thing. If you have any recommendations, I would love some suggestions.

3. I do concede that I was having a difficult time coming up with a capstone. I wanted something that allowed for more network building, but I already did that with the level ten feature, so I was at a bit of a loss. I'm thinking of maybe making it more of an area control for some more mechanical flavor, but I am not decided. 

4. It is true that the aura theming is a bit vague, and so my next order of business will be to add more "flavor" paragraphs to make it pop (similarly to how Moon Druid doesn't really have its own wild shape feature but relies on the spells and extra description for its theming). Plus, I don't have any art so that certainly doesn't help. I think what I was trying to get at was someone who flies through the auroras and uses it as their magic, but I'll try to make it come out more clearly in my next iteration. 

Thank you so much again! I'll make sure to make a few edits to the original as soon as I can.