In the year FA 496, when Túrin Turambar came to Dor-lómin seeking news of his mother Morwen and sister Niënor, Túrin found the region under the control of Brodda the Easterling, who had taken Túrin's kinswoman Aerin as wife. Túrin killed Brodda in anger, instigating an uprising against the region's Easterling rulers. Learning his mother and sister no longer were present in Dor-lómin, Túrin departed, accompanied by Asgon and several others who had taken part in the uprising. Túrin left those who followed him in the mountains, but not before Asgon reminded Túrin of the hardship he had brought upon them, and warned him not to return unless it was to free them.
After Túrin's death, Morgoth released Túrin's father Húrin from captivity in the year FA 500. Húrin traveled to Hithlum, where he met a small band of men led by Asgon, who gave Húrin an account of what Túrin had done in Dor-lómin. Asgon and his men would follow Húrin to confront the Easterling chief Lorgan, though little would come from that meeting. Húrin would leave his followers soon afterwards while they slept, travelling into Dimbar. In Húrin's absence, Asgon led the others into Brethil, where they were captured, but eventually released by the Haladin. Asgon, believing Húrin would one day return to Brethil, set a watch on the forest.
Asgon's fate afterwards is unknown.