Geological / environmental event
The creation of the Savage Isles left many mortals with questions. For the dwarves of Du'merh that question was mainly "how can we profit from this" and soon after they profited massively as trade increased to these strange new lands where metals were needed for weapons of war.
With the creation of the Savage Isles the kingdom of Du'merh were quick to seize any opportunity they could. Unfortunately they were not quick enough to colonize the lands themselves as they had only recently settled in the mountains and the savage isles were soon filled with strange new creatures that each battled for superiority over the other. Although many of these creatures were animals unable to communicate, some of them showed considerable intelligence and soon began trading food, salt, and wood for dwarven weapons which they in turn used to conquer more of the savage isles, which then in turn required more weapons to defend. Like this the dwarves of Du'merh equipped all sides of the conflicts and profited massively in its early years.