The Creation of the Material Planes

Before the creation of the material planes, the other planes in the universe kept relatively to themselves. With the exception of the celestial and infernal planes however, who wage a constant war between their planes throughout the Astral Plane. The celestial and inferal planes were not involved with the creation of the material planes though, at least not at first. Instead, it was Aedifidea - Planar Architect and Tempmet - Time's Arrow / Moons' Keeper, the two deities who rule over Pinnacle, who had the idea to create a brand new plane.
Pinnacle is a "perfect utopia" of a plane in the Astral Plane by Aedifidea and Tempmet's standard, but it is the smallest plane in the universe, a gargantuan metropolis, but still tiny compared to the other planes. Because of this, the two deities decided to try and take what they've learned from the creation and ruling of Pinnacle and upscale it by creating a new perfect plane more of the size of the elemental planes.
Aedifidea, with power over creation and space, began to borrow elements from each of the elemental planes to shape this new plane. The creation of an entirely new plane did not go unnoticed for long however. The first other beings to arrive to investigate were entities of pure chaos from The Turmoil. Almost immediately they began to interfere with Aedifidea's work, so in an effort to distract them Aedifidea abandoned this first draft of the plane and granted it to the beings of chaos to do with as they pleased. This plane later became known as the First World and the beings of chaos became the archfey and deities known as The Firstborn. Soon after this, more deities came to try and exert their own influence over the new plane being created. Beings from each of the elemental planes, the celestial and infernal planes, even entities from The Expanse, The Void, and the Astral Plane tried to make their presence known. Aedifidea tried to keep all of these beings busy so they could focus by granting them their own drafts of the plane, this lead to the creation of the Netherworld and the Ethereal Plane, but in the end it was all for naught. Despite their best efforts, Aedifidea succeeded in creating a new plane but it was not the perfect utopia they and Tempet had invisioned, it was instead the new Material Plane. A single massive continent by the name of Vylderaine.
After the creation of the material planes and the Primordials had populated them with fragments of their being, the gods all mutually agreed to take a step back and watch and influence the planes from afar (similar to an art farm), the only exception to this was Sinavāḍu - The Overseer / All Knowing who decided to move their domain from the Astral Plane to the Etheral Plane in order to watch the events of the planes unfold more closely. Things continued to develop on the material planes as normal, until the events of The Schism occurred.