Nivemus should get Oberndorf... If you want to talk history, the region belongs to either Old Rancagua, Sirion, or Fontan. Jor has been trying to say Westmoor has a claim but we all know it's BS.
Also, to go back to Sirion vs Fontan, several factors went into making Sirion a powerhouse that could withstand 5 realms. First was geography. Second, stupid tactics(seriously? You are going to attack Trinbar again and not go up through Avamar? How predictable...
). Third the fact they were heavily bolstered by war-lusty nobles and former Old Rancaguan nobles. Lastly, because coordinating five realms across nearly the entire continent is a difficult thing to manage at best, and even harder when two of the stronger ones are so far South they can only come every other week.
That, in a nutshell, is how Sirion withstood the onslaught and later used that momentum to turn the tide of the war. Other factors were of course involved, but those were the big ones.