IIRC, it was possible to secede and create realms. Isn't that how Toren was created on both SEI and SWI? Thing is there were only 3 cities and a stronghold. And since three of them were occupied by pre-generated realms, that doesn't leave much room for expansion. :p
Toren was created by Tom as a fourth realm after the first SEI war ended. Secession was in fact possible though. In the second war, Sandalak City seceded from Ikalak and existed as a separate realm for a while until it was taken back by Ikalak.
