The Veil

When the world of Amion was created, The Gods of Avalyra were able to physically manifest upon the material plane, and many did so to lead their followers in direct fashion. Particularly the likes of Valdir  and Yreus, who lead vast armies across the world, conquering huge swathes of the world, and sowing chaos as they went. Many of the other gods shaped parts of the world in their own image, leading Sirona to despair as the world they all worked together to create was slowly twisted by gods' selfish desires. Without the power to directly stop the changes and chaos being wrought by her children, the Ancient Mother instead drew energy suffusing the world, both positive and negative, and weaved that into The Veil. A plane of pure energy, she interposed it between the material plane and the planes of the gods. As she did so, she cast the gods back to their planes, and sealed them there using the Veil; the torrents of positive and negative energy preventing the gods from directly interfering in the mortal realm. In the millennia since the Veil's creation, the gods are limited in their interactions, having to influence the world through champions and guiding other mortals into doing their bidding.
Those who have survived contact with the Veil speak of a swirling nexus of pure white and black energy, forever shifting in wild and unpredictable ways. There is no sense of direction, only an endless, ever roiling sea of two clashing colours. Without incredible protection, any individual who finds their way into the Veil will be simultaneously ripped apart from the very base of their being by negative energy, while being fully restored by the positive. The pain of this is enough to drive almost any creature to insanity in minutes. Luck then governs how long they will survive before they are overwhelmed by either positive or negative energy, and wiped from existence, becoming one with the plane itself.
Some rumours persist of gods that either escaped Sirona's sealing, or have been able to pierce through the veil in the time since its creation. The most common among these concern Rymos and Etyx, Lumir's 'failed' twin.  They rule over The Feywild and The Shadowfell respectively, each a distorted mirror of the material plane. Many scholars insist that these planes are not affected by the Veil, instead laying across the material plane like a blanket, and that the two deities could, should they desire, manifest in the mortal world. Additionally, Etyx is said to have created The Forgotten Isles as a refuge for herself upon the material plane. Utilising the cover of The Shroud, it is said she escaped Sirona's notice, and remains in the Isles to this day, with the Ancient Mother now powerless to pull The Shadow back to her own plane.
While most literature agrees that the Veil is entirely impenetrable, even for the gods, there do exist theories that it could be pierced. The most common of these holds a simple idea; if a god can amass enough power, they could pierce the veil, effectively blasting their way past the torrent of energy. The effects this may have on the god, the Veil, and the other planes is unknown, with theories ranging from little effect on any, all the way to a collapse of the entire planescape. No records exist of this having happened, with the Veil holding firm since its creation, but certain groups have attempted to allow their gods through in various ways.

Type

Dimensional plane

Overseer
Sirona
Time
Normal
Gravity
None