Humans ruined everything. They showed up on the planar scene a little over two hundred years ago and immediately seemed like a breath of fresh air to the culture and economy of the Dodekapolis. Their trade fleet expanded across the astral, they established banks in every city, and it wasn’t long before their language became the lingua franca of business and diplomacy across the planes.
About fifty years ago, humanity began a project building an astral highway network of sorts they called the Deepline. The project was led by the finest wizarding minds humanity had to offer, the Diametric Chamber. Led by archmage Simon Vance they made incredible progress and city after city was connected to the network. It was not only faster and safer than ship travel through the shallow astral, it eliminated the need for navigators.
No one’s quite sure how or why it happened, but the energy source for the Deepline went critical three years ago. Conspiracy theories abound as to foul play and who might’ve had the means and motive of doing such a thing. The entire web of deep astral pathways collapsed, sending ripples across the planes, killing everyone who was in it at the moment of failure. It destroyed massive swaths of ports across the Dodekapolis, killing billions and destroying any ships docked there.
The multiverse hasn’t recovered and it’s unclear as to whether it can. Astral travel is now nearly impossible as the foundations of planar connections is rooted in the deep astral. It’s unknown whether damage to such a fundamental building block of the planes can be repaired.