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 upland flowing Anzar glacier. The river carves a tunnel under the ice as it flows downland; counter to the glacier which flows upland towards the Giant Steps mountains. Passage is slow and dangerous for boats taking this ten mile journey. Stops to clear low hanging ice are often required and the danger of falling ice shards are 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.