This endless mountain range was called Cloud Mountain. If one wanted to circle around it, they could either head northwest and pass through the White Knights' sphere of influence or head southeast until they reached the Great Plains, where the terrain eased. That was the front line of First City's confrontation with the Salvation Army—it was the former's Eastern Army defense zone.
In the Old World, Cloud Mountain wasn't an insurmountable natural stronghold. Many bridges and tunnels connected the two sides, but many bridges had collapsed, and many tunnels were now blocked. Only a few remaining routes allowed passage through the mountains, and these were guarded by First City and the Salvation Army.