Dwarves

As the Dragons warred overhead, and orcs emerged from the Underdark, the Dwarves retreated back down to their ancient Dwarven cities. This gave them the safety they needed during the Great Cataclysm while huge fireballs and bolts of lightning rained down from the skies. It also afforded them strategic bottlenecks to defend themselves.

Any mountainous ranges on the Isles is likely to connect to a complex underground network of caverns and paths (known as the Underdark). The Dwarves have remained underground since the Cataclysm, wary of anyone or anything coming from the surface. They are not as isolated as the Elves, however. Their primary concern was safety, but they have re-built their underground cities over the past several decades, and they are arguably the most prosperous of the races on the Isles.

The Dwarves accomplished this advantage by enabling the Orcs. The Dwarves became slavers, capturing Goblins and other underground creatures, domesticating them (although they don't discuss their methods with outsiders), and selling or trading them to the Orcs who remained above ground. The Orcs have become dependent on this flow of "disposable" workers, relying on a blatantly one-sided trade agreement the Dwarves constructed. This keeps the Dwarves relatively happy, fed, and rich... as long as the Orcs depend on the trade agreement. Some have speculated that the Dwarves may even be orchestrating the Orcs' dependence, but evidence is in short supply.