Plaguelands Civil War The Plaguelands Civil War was a civil war fought primarily between the factions of the Undead Scourge , the Burning Legion , and the Forsaken / Alliance . Its events were chronicled from " King Arthas " to " A New Power in Lordaeron " . Prelude . While Archimonde was defeated and killed by the Great Alliance during the Battle of Mount Hyjal , the remaining dreadlords of Lordaeron , Bal ' nazzar , Detheroc and Varimathras were not informed of their master ' s defeat . What they did not know was that Archimonde ' s death gave more leeway for Ner ' zhul to act . This along with the growing resentment of Scourge figures such as Kel ' Thuzad only worsened the potential situation the dreadlords could find themselves in . King Arthas . Breaking into the dreadlords ' chambers , Arthas proclaimed the defeat and death of Archimonde , and manages to scare off the three dreadlords . Declaring himself king , his first order is to purge the remaining humans of Lordaeron . Despite the arrival of the paladins , Dagren the Orcslayer , Magroth the Defender and Halahk the Lifebringer , Arthas and his men are able to kill the latter two and eliminate nearly every human in the kingdom . During and after the battle , however , Arthas suffers numerous head pains , with the Lich King stating that a " danger " was coming to Northrend , and that Arthas needed to come and rescue him . Creation of the Forsaken . Because of the havoc at Northrend , the Lich King ' s powers dwindled along with Arthas ' , and this caused some of the undead Scourge to have their own , independent thinking . Having regained her own sentience , the Dark Ranger , Sylvanas Windrunner was approached by the dreadlords . The dreadlords staged an ambush against the new king at Capital City , but Arthas is able to evade their grasp . Reaching the outskirts of the city , Arthas is deceived by Sylvanas ' banshees and lured into a trap , but the timely arrival of Kel ' Thuzzad saves the king , and Sylvanas is forced to retreat . While Arthas completes his preparations to leave for Northrend , Sylvanas begins to ponder on her newfound freedom . Approached by Varimathras to serve the Burning Legion , she rejects his offer , and the two square off at the Trisfal Glades . Despite her numerical disadvantage , Sylvanas prevails by having her Banshees possess the numerous units within the area ; including the ogre warlord Mug ' thol and Snarlmane . The defeated Varimathras pleads for his life , and promises to give Sylvanas vital information regarding the defenses of his brothers . Joining the Dark Ranger , the two reach Detheroc ' s base at the Western Plauguelands , and quickly find that Detheroc has possessed the human leader , Lord Garithos . Making use of the cover of night , Sylvanas ' forces are able to take their enemy by surprise and score another major victory , killing Detheroc in the process . Upon Detheroc ' s defeat , Garithos and the humans under him are freed from the mind control , and aid Sylvanas ' forces in attacking Bal ' nazzar ' s forces at Capital City . Forming a joint attack , Bal ' nazzar is seemingly killed by the combined forces of Sylvanas and Garithos , but she quickly turns on the human commander , and she orders that Varimathras kill him . Establishing her forces as an independent faction , Sylvanas formally declares the formation of the Forsaken , a group of undead independent of the Scourge .