The latest update to the WAR Herald brings a new FAQ on the upcoming Land of the Dead expansion.

Q. How do I travel to the Land of the Dead?

A. You will be able to fly to the Land of the Dead after you unlock the Flight Path by speaking to the Flight Master in your capital city. Once you unlock the flight path to the Land of the Dead, as long as your Realm holds control, you can fly there from anywhere in the world! Keep in mind, you will only be able to fly to the Land of the Dead if your Realm controls it. In the event that the population cap has been reached in the Land of the Dead, your Flight Master will inform you of such.

Grab the FAQ here.