Reminds me of a setting I wrote up but never really got to use.

Set immediately after the Godswar. The world was in chaos, the landscape constantly twisting and changing. People, creatures and monsters changing with the environment. You might be a wood elf today, but suddenly you are at the bottom of the ocean and you are a sea elf...
There is a solution. Wizards and clerics working together have found a way to stabilise, and even lock down small chunks of countryside. From a simple ritual that protects your campsite, up to the mighty pylons that anchor entire counties (about a 32 mile hex).

There is a lot of Birthright style realmbuilding, with the added advantage of being able to add exotic terrain features, or resource rich provinces to your realm...or even just sending out teams to harvest/pillage the surrounding landscape before it warps into something new.

Of course any new change brings the threat of new and warped monsters...