Here in the Zone, preventing extraplanar invasions is of paramount importance. We keep tight control over teleportation, summoning, and other similar magic by installing teleport sinks in each of the Embassy Cities that trap unauthorized transpositions.
Back when I was a zap I loved Sink Duty! You got to stand outside a warded cage of cold iron with a pike and permission to poke whatever popped in! You never knew what you'd get, everything from shadow bogies, to wild winky dogs, or unsuspecting mist stepping thieves!
The world of Erathia is constantly under the threat of extraplanar invasion from the Kirinal Pit. The great fortresses around the Pit prevent traditional invasions from simple armies. The teleport sinks trap invaders who try to teleport out of the Pit and into the wider world.
They divert teleportation by exploiting the dimensional "heaviness' of the Pit itself. Each teleport sink uses unique properties of the Pit to create a "funnel" that pulls extradimensional travelers into a particular point in the Zone. This method of mass diversion only functions relatively close to the Pit. Each Canton is responsible for maintaining a teleport sink that covers their slice of the Zone.
The sinks empty into highly secure detention centers in the Embassy Cities. Unauthorized teleporters materialize inside cold iron cells hardened with heavy magical wards and surrounded by protective circles. Guards monitor the cells for incoming "jumpers" who are thoroughly questioned upon their arrival. These jumpers have to pay a fine and may possibly face jail time before they are released or returned to their point of origin.
Any teleportation or conjuration effect cast with an origin or destination inside the Kirinal Concordance Zone and over a distance farther than 25 feet is diverted to the nearest teleport sink. Teleport sinks are located in the Pit-ward side of each of the Embassy Cities.
A 30-mile hole in reality ringed by fortresses and cities. The world's greatest threat and resouorce.
Kirinal Concordance Zone
The neutral zone around the Kirinal Pit. It's divided into 8 allied squabbling city-states.