When Túrin Turambar gathered the men of Brethil together in Ephel Brandir, calling for warriors to accompany him in his attack on Glaurung, Dorlas was the first to join. With no other volunteers forthcoming, Dorlas taunted Brandir, asking in a mocking tone who would take the latter's place in the party so that the House of Haleth would not be put to shame. Offering himself in the stead of his kinsman Brandir, Hunthor rebuked Dorlas and warned him against speaking evil of the leader of their people.
In hot pursuit of Glaurung, Dorlas and his two comrades came to Cabed-en-Aras and descended the perilous cliff while the river waters of the Taeglin roared below. However, when it came time to pass through the wild, rock-filled water, Dorlas quailed in fear and remained behind while Hunthor and Turin crossed to the opposite shore.
Hiding in shame in the nearby woods, Dorlas was eventually found by Brandir, who quickly perceived that Dorlas had abandoned his companions and their mission in fear. Blaming Dorlas for Níniel's suicide, Brandir stabbed Dorlas just as he was about to punch Brandir.