The Frost Dwarves who lived amid the bitter winds of Stormcrest were distant kin of Azeroth's dwarves. For generations, they had inhabited Frosthold, a fortress built of ice and snow, and they were embroiled in a civil war that had lasted hundreds of years. Their enemies were their own brethren, the Iron Dwarves of the Thunderforged Legion. Despite their mastery of frost magic, the Frost Dwarves were losing the war. During an expedition, their elder discovered a Flesh Dwarf who had lost his memory. Though this hero had yet to recover from his wounds, he used Avatar during an Iron Giant attack and single-handedly drove off the invaders. From then on, he was nominated as the new king of the Frost Dwarves. He was Yorg Stormheart-the amnesiac Mountain King, Muradin Bronzebeard.
That was the history of the Frost Dwarves in the original timeline.
But in the Azeroth where Rex lived, their history had long since changed. They had established ties with him very, very early on.
It had been shortly after the outbreak of the Undead Scourge. While forging the Ashbringer, Rex had made a special trip to Northrend. To obtain the Bronzebeard Dwarves' help, he had revealed what had happened to Muradin, then traveled to Northrend and established contact with the Frost Dwarves. They should have remained locked in endless combat with their mortal enemies, the Harbor Iron Dwarves. Instead, their connection to Rex had brought them considerable aid, especially from Ironforge.
Because of Muradin, Ironforge had already come to regard the Frost Dwarves as allies. With resources supplied by the Kingdom of Gilneas and Ironforge, the conflict between the Frost Dwarves and the Harbor Iron Dwarves had been settled in just a few years.
Naturally, the Frost Dwarves had won. There had never been any doubt about that.