Metropolis Manifest Treaty
Some worlds that have Manifested in the Kirinal Pit are selected as trading partners by the Concordance for Survival. Those that agree to sign the Metropolis Manifest Treaty are given a Lodestar Beacon that the Orrery of Worlds can home in on. Then, on a pre-arranged day, the designated area of their world becomes the Manifest. Over the decades, these Days of Trade have become profitable for everyone involved.
You don't actually have to be a big city to be offered a Metro Treaty but it definitely helps! We actually named them after the first big city to sign one! It was one of those "Dirt" worlds that the Isekai come from! They worship this Big Blue Boy Scout over there who gets excluded by the Divine Gate whenever they Manifest. He sounds like a great god, I'd love to meet him!
The Concordance for Survival offers potential trading partners the option of signing a Metropolis Manifest Treaty. For the world in question, this can be a life-changing event, giving previously non-magical worlds access to a multiverse of goods.
The Concordance created the Treaty for a variety of reasons. Mainly, having a stable world for the Orrery of Worlds to focus on decreases the chances of a hostile world from manifesting in the Kirinal Pit. Secondly, there's the mutual benefit of having a cooperative trading partner out in the multiverse that is expecting to be Manifested.
A Signatory World is expecting to travel across the dimensions and instead of spending half a day explaining what has happened and calming down a frightened populace, a Day of Trade can commence immediately.
Lodestar Beacon
Each Signatory World receives a Lodestar Beacon, a magical device that allows the Orrery of Worlds to pinpoint their location and facilitates a smooth transition as the Signatory manifests in the Kirinal Pit.
The Lodestar also acts as a focus for those with the ability to travel or communicate between worlds. The Lodestar can be deactivated from either side and part by Treaty, the Signatory or the Concordance can destroy the Lodestar at any non-manifest time for any reason.
Manifest Security
As illustrated by the debacle around the Hell Week Accords, the Treaty can be abused by either side. Invading armies, plagues, or disasters of any kind could preclude the Day of Trade from happening.
The week before the pre-arranged Treaty Day, ambassadors are exchanged between each world. Both are given a device to deactivate the Lodestar at any time if they feel the need. Usually, these are merely ceremonial visits full of feasting and celebration.
On Treaty Day, the Kirinal Defenders still man the Pit Wall, but they do so in ceremonial dress to welcome the new metropolis.
After a few bad experiences, the Kirinalos make sure that their weapons are actually ready and loaded, just in case.
I like your descriptions of how this is a bit of a double-edged sword.
Thank you! I'll probably expand on this after Summer Camp.
Take a look at my Institutions of Learning challenge article.
Learn about the World of Wizard's Peak and check out my award winning article about the Ghost Boy of Kirinal!