Dwarves made Svinga and Iomega habitable by creating elaborate tunnel systems and underground cities, because the surface is unbearably hot most of the year. No one is sure where the dwarves lived before they came to the island, including the dwarves themselves. The ruins at Merzi and Oblee are the only evidence the dwarves ever tried to live on the surface.
Iomegan dwarves are more insular and focus on mining and hoarding wealth, trading with Svingans when necessary.
Svingans generally consider themselves brokers of the Iomegans labors. The port at Tiru is a major trade point and is famous for being the world's only underground seaport, located in a massive dwarf-made cavern.