Detheroc along his brothers Varimathras and Balnazzar were sent by their commanding officer Archimonde to watch over the Legion's fortresses in Lordaeron when he leds his forces to fight against the orcs and night elves in Mount Hyjal. After the Third War, Detheroc realized that it has been a long time since they heard from Archimonde.Arthas Menethil came one day and attempts to take over their holding and told them that the Legion was defeated. Before the death knight could attack, Detheroc and his brothers retreated and made a deal with Sylvanas Windrunner to help them reclaim their bases from Arthas and his minions. With his brothers, Detheroc attacked the Capitol City and faced Arthas. However, the death knight retreated to his master in Northrend after hearing his call.
After Arthas retreated, Varimathras offered Sylvanas to join their new order. She refused the dreadlord's offer and attack his forces. Sylvanas however spared Varimathras in exchange for his loyalty which the demon accepted. Detheroc, outraged at his brother's treachery brainwashed a human general Garithos thereby commanding the general's forces. He later send Garithos and his men to attack Sylvanas. However, Sylvanas managed to hold off Garithos and tore Detheroc to shreads. However, it is suspected that Detheroc was banished to the Twisting Nether and that he might return someday.