Ethereal Veil

The Ethereal Veil is a plane that overlaps with other worlds.

Traits

 * Planar transparency: It is possible to see into any adjacent planes from the Ethereal Plane.
 * No gravity: It's like swimming underwater but with no feeling of weight or buoyancy.
 * Adaptive time: Time moves with the same speed like whatever plane it is adjacent to.
 * Infinite or Finite Size: The plane's size depends on which plane it is adjacent to.
 * Magic filter: Magic inside the plane can be cast normally but no physical effect cast there can affect any adjacent plane, although mind- and force-based magic like Magic Missile can phase through.

Links to other planes
The Ethereal Veil overlaps with most other dimensions, allowing it's inhabitants to see into them like through a oneway-mirror. Someone in the Ethereal Veil can phase through walls they see in the Prime Plane just like someone in the Prime Plane isn't affected by any object in the Ethereal Veil. Creatures can't physically affect each other through the planar boarder, but it is possible to interact trough certain magic.

It's possible to perceive adjacent planes through acoustics and vision, but sounds are muffled, colors are muted and the overall sight is blurred. Fine details like the writing in a book can't be discerned. Moreover, it's impossible to see further than 60 feet into another plane.