I've been working on this spell for the last few days, and i'm wondering how I can improve the mechanics/lore of it.

1. I was thinking of maybe adding some lore, like the plane has remnants of other worlds scattered across the plane, maybe there's treasure to find, or players have to go to a particular place in the material plane to find some item or structure that exists in the Aether

2. The mechanics of the still seem vague, the phasing doesn't really make sense, and also it's pretty much just dashing as a bonus action.

I would really appreciate some feedback  

https://www.dndbeyond.com/spells/1097043-aether-shift

1. I have an idea for some lore! Maybe use something like Karsus' Folly in 4e. Basically, an extremely powerful mage or demigod decides to change the fabric of reality, and creates a calamity because of it. Maybe Mr. Calamitous Wizard wanted to create a plane of his own, by fusing together all the other planes into something new that he could rule, the Aether Plane. When he did this, however, he could only finish some of the job before it killed him from the stress of making a plane. Because of this, the plane is unfinished and unstable. Whenever a creature attempts or does actually enter, it, the must make CON saves to avoid being thrust out into whatever plane they came from. The Aether could replace the plane of Limbo (Google it) in your world, as it has more flavour that way. It could also be a cool way to start a campaign, like the unstable plane is yanking things through to itself, and threatens to destroy the Material Plane. The Aether itself is a sea of chaos, while resembling the Material Plane. It has all the structures of the Material Plane, while sudden volcanic eruptions, tornadoes, earthquakes, and tsunamis plague it from its fusion with the Elemental Planes, as well as others. You may also spontaneously teleport around, fly, or suffocate while in the Aether. This could pose some danger to those who enter it via Aether Shift.

Mechanically, it does seem a little like dashing, or like the Blink spell, but I think I can help! How about these changes: While in the Aether via Aether shift, you appear as a shimmering blue blur, but are still able to be attacked, as you only enter the Aether partly, and have a semi-physical form. You can walk through solid objects in this form, but every 1 foot costs 3 feet of movement. At the start of your turn, roll a d4. On a 1, you teleport to a random location within 10 feet that the DM decides, due to the Aether's unpredictability. On a 2, you take 1d6 damage of the DM's choice, or of random choice, due to the chaos of the Aether. On a 3, you fly up 10 feet, like you had the Levitate spell cast on you. On a 4, you are blinded until the start of your next turn. While in the Aether, all attacks also have disadvantage against you. At the end of your turn, make a CON save of DC 12. On a failure, you are ripped from the Aether and take 2d4 force damage. If you end your turn within and object, you take 2d8 instead.

Sorry this was so long btw, but just some of my thoughts on how it could differentiate itself from Blink and other ethereal-type spells :)

Thanks for all the awesome ideas!! The concept of the Aether pulling in pieces of the material plane actually works rather well for my world. Also the teleportation effect seems like it could lead to some very weird situations that could be quite amusing lol.

I'm glad I could help :)