Astral Plane

The Astral Plane are the transitive planes between the inner material and elemental planes and the outer Spectral Planes.

The Astral Season
At first the plane would appear like a vast silvery mist, impossible to penetrate with any light, however after enough wandering an astral traveler would find themselves in the world they left except for change in odd and peculiar ways. All liquids would be replaced with a syrupy silver liquid and where there normally would be landscape is only dense fog or mist depending on the "season".

Unlike the other planes in the Prism, the Astral Plane doesn't physical move or rotate in any way, it remains completely stagnant but pays the cost of endlessly shifting between four different transitive planes, each a strange and hollow reflection of the world the traveler has come from. The world turns grey-scale as the season winds down, on the final day spectral wells in hidden locations open up around the world revealing passages to other plane (or even dimensions), each their own hue hinting at the location on the other side.
 * The Springrise, fey and trickster spirits pull the puppet strings of foolish decoys of the reality you once knew. All non-player inhabitants are children or babies.
 * The Summerlands, the fey wither and die and the world softly melts in the endless heat. Everyone is agitated and all non-player inhabitants are either emotional teens or desperate adults.
 * The Madseason, merciless bad weather pummels the world; endless debris perpetually falls from trees or actual disasters like tornadoes or hurricanes. All non-player inhabitants are elderly that are extremely feeble-minded and quickly die to old age or from the storms.
 * The Hauntbarrows, a world of endless winter with mounds everywhere you go accenting the countless dead. The barrows move under the cover of night and player wake up surrounded by them. All non-player inhabitants are dead.

''If the player simply wanted to return to the Material Plane fully submerging themselves in the silvery water will send them back to the material world they came from. These ways of transition would remain open until the new dawn brought the Springrise again''.

Breaching the Veil
Though these four strange mirrored planes of the Material Plane were mostly contained to their astral domain, once every now and then each of the four seasons could pass through the veil that normally separated them from the material reality. It was during this time that several monster species including the aberrations, celestials, monstrosities, elementals, fiends, and others would find new homes away from the relentless cycles of the astral seasons.