Built into the cliffs of the Storm Coast, the port at Daerwin's Mouth once connected the dwarven thaigs to the Waking Sea. In addition to increasing trade between the dwarves and their allies in the Tevinter Imperium, direct access to the Deep Roads meant diplomats from Orzammar could visit the port without fear of losing their "stone sense." The site thus became a popular meeting place for ambassadors of the two nations.
When darkspawn incursions forced the dwarves to retreat into Orzammar, the Deep Roads leading to Daerwin's Mouth were sealed and the port fell into disuse. At least, all reputable use of the port ceased—bandits, smugglers, and pirates are known to use the various caves along the Storm Coast, including Daerwin's Mouth itself, for their own gains.
—From The Storm Coast and Its History by Brother Vincent, Chantry scholar