The headwaters of this northerly flowing river begins at Mazgob. Going north from this swamp, the river flows past the towering walls of Midrurgrune and then into the reverse flowing Anzar Glacier. The river naturally carves a tunnel through this ice, but help is needed for the passing of ships. A ten mile journey, stops to clear low hanging ice are often required and the danger of falling ice shards ever present. Once past the glacier, the river flows into the swamp Guivre and then joins with the wide waterways of the Famirótan river.
Irudrarg is a major waterway for traffic going to and from the Orchish Empire.