100 years after creating Darlung, Sauron made him the chief of the orcs in the fortress of Dor-Lun. Darlung's host defeated many of Sauron's enemies and caused damage to many Kingdoms. After Sauron's defeat in the Battle of Gorgoroth, Darlung made himself king of Dor-Lun, he soon made alliances with other evil creatures that lived there (Spiders Bats, etc).
Battle of Five Armies
During the Third Age, Darlung joined Bolg's forces in the Battle of Five Armies, he killed many dwarves, elves and men. He almost killed a Great Eagle, hiting the Eagle´s neck but the eagle was saved by Thorin Stonehelm who pushed Darlung out of mountain. Darlung and his remaining forces retreated to Dor-Lun.
War of the Ring
In the end of the Third Age, Sauron returned and is again causing trouble to Middle Earth. Darlung who after hearing the news of his master's return, travelled to Mordor. In Mordor, Sauron ordered Darlung to come back to Dor-Lun and destroy Lake-Town. He attacked Lake-Town and his army almost destroyed the city but King Dain and a dwarven army arrived and drived the orcs back. Darlung survived, but lost one eye.
After Sauron's death, Darlung attempted to avenge his master's death by attacking Dale. His army layed siege on the city, Darlung almost killed Bard II but in the moment he was going to kill Bard II, Thorin Stonehelm arrived and beheaded the Orc Lord.
After Darlung's death. His second-in-command Garbunz became the Lord of Dor-Lun