This was originally going to be a multicolor card that shrank a creature (black) and did prevented it blocking (um), but all the ideas I could think of could be done best by black. Again, very close to existing cards, and very similar to vertigo, but either is something the set should have.

Originally the flavour was of an Aeran exiled; now it would make more sense to change it to an Aeran ambushed by black creatures.

Maybe a bit too powerful when compared to Last Gasp, but that's not what I should be focused on.

I don't know. It does seem a bit too close to vertigo to me. I know black doesn't naturally have 'anti-flying' clauses, and we need black to have an anti-flying clause, somehow, in this set. I'll have to remember to dig hard and see if I can get one. Maybe it can be "Destroy target multi-colored creature"?

Ooh! How about "Target flying creature loses flying, then deals damage to itself equal to its power." It's reminicent of Kiku's Shadow so it's been done before, and has a flavor connection of smashing something into the ground (dragging it with black tentacles?)

Why does no one ever complain that Vertigo is too close to Earthbind?

For the same reason most people don't complain that Tor Giant is too close to Hill Giant, I suppose. Vertigo was just a 'fixed' Earthbind for a set where they felt that they needed to replicate early Magic. It's supposed to be too close to Earthbind.