Feysky

The Feysky is the infinite sky of the Feywild, roughly analagous to the Underdark of the Shadowfel. It is divided into five layers, outlined below. Each layer has at least three names: one long scientific-sounding one used by the Gnomes and several more desciptive ones used by the other inhabitants.
== The Geozephrium/The Dirt-Sky/The Earth-Sky ==
This is the sky 0-10 km from the ground. It's effectively just "normal" sky, as would be found in the Fadelands, although weather from the Epizephyrium affects the climate somewhat.
== The Epizephyrium/The Low-Winds/The Inner-Sky ==
At this level, regular flight magic stops working properly - a standard level three flight spell just counts as feather fall and level 6+ flight spells just count as levitation. In order to fly proplerly, you need a flight spell with the "zephyric" modifier.
Wings still work, but the distances between things are so great that even rocs have difficulty living here. There are some solid clouds, occasionally supporting plant life.
This is also the lowest layer at which sparkdust can function.
== The Latazephyrium/The Free-Winds/The True-Sky/The Wide-Sky ==
At this level, regular flight magic does absolutely nothing at all.
The Latazephyrium is home to floating islands made of formerly-living beings, sort of like coral reefs, which encapsulated planar energy during their lifetimes. It has been confirmed that these do not degrade or leak energy, making them effectively permenant structures.
This is also the layer in which Gif, Tabaxi, Aarakocra and Grippli can be found.
== The Circumzephyrium/The Choking Winds/The Hollow-Sky ==
At this level, zephyric flight is affected in the same way that terrestrial flight is in The Epizephyrium, so you need void flight, although these don't work at lower levels. More floating islands, even mountains.
== The Archalozephyrium/The Void/The Dead-Sky ==
At this height, all non-void flight magic does nothing. This is effectively outer space, with no breathable air at all, barely any light (none at all at night, only sun-side of objects visible during the day) and incomprehensibly large distances between things. Things may live up here, but there aren't other planets or anything. Note that even at this height, the stars cannot be reached, unless you're The Tall One.