Emerald Nightmare The Emerald Nightmare ( or the Nightmare for short ) is a mobile area of corruption within the Emerald Dream . Despite the defeat of Xavius and the removal of much of the nightmare through the course of the events described in " Stormrage " , players will get to experience the Nightmare in Val ' sharah with the release of the expansion Legion . Nature of the Nightmare . The Emerald Dream is not a place of total perfection . It can be shaped and twisted by dreams , usually without a sleeper ’ s knowledge . Sadly , nightmares are themselves a crafting of the subconscious and have given rise to their own place within the Dream . The Nightmare , as the denizens call it , is not a specific location , but a constantly roaming effect that travels about unpredictably . The skies above the Nightmare are constantly clouded , creating a gloomy , depressing zone that weakens and deadens everything it touches . The beautiful green vegetation is twisted into brown decay , while ordinarily peaceful creatures are corrupted into shadowy , mutated versions of themselves known as Corrupted Ones . The Corrupted Ones are vicious and cruel , hunting anything they can , even after they leave the Nightmare ’ s affected zone . Worse still , some dream - travelers who enter the Nightmare — or are engulfed by its movements — become trapped in the Emerald Dream . They cannot leave , so their bodies back on Azeroth remain in a permanent sleep , slowly starving to death unless tended by helpful aides . While trapped , they are known as the Unwaking ; they are also corrupted , and will do anything to get back home . The Nightmare is believed to be slowly growing in size and power . History . The exact origins of the Emerald Nightmare are not entirely clear , although it is stated by the whispers from Xal ' atath , Blade of the Black Empire that it was created by the Old God , Yogg - Saron . The reasons why the nightmare has become so strong in recent years was long unknown . Although Xavius did not create the Nightmare , he came to rule over it as the Nightmare Lord . Xavius orchestrated the corruption of the Emerald Dream by manipulating Fandral Staghelm into planting a branch of Xavius ' s own tree into Teldrassil , ensuring that the new world tree would be corrupted from the start . His plans culminated in a daring attempt to bind Azeroth and the Emerald Dream into one plane , seizing control of Azeroth ' s residents while they slept and giving shape to their nightmares . Xavius himself was a minion of a powerful yet ancient evil ( confirmed to be N ' zoth ) . Despite Xavius ' defeat at the hands of Malfurion Stormrage and his allies , the Nightmare was not entirely destroyed following its master ' s defeat . One small part subbornly stayed in the Rift of Aln , and Malfurion could only seal off the vicinity around the rift until a time that another war would be in their favor . The Nightmare ' s influence in the Barrens following the Cataclysm suggests that the evil controling the Nightmare may have taken advantage of the event to attempt to infect Azeroth once again . Many druid s are called to the Emerald Dream to help fight back its effects . So far , the green dragons have done what they can , though they dare not risk becoming themselves corrupted . The Eye of Ysera has not yet been approached by the Nightmare , but some fear that one day it will . + In World of Warcraft . The Nightmare is created using the twisted thoughts and fears of sleeping beings ’ subconscious minds to corrupt the Emerald Dream . It travels slowly through the Dream , leaving corrupted , vicious animals and Unwaking travelers in its path . The Night Elf druid Naralex and his former acolytes in the Wailing Caverns have been corrupted by the Nightmare - transformed into the wicked Druids of the Fang . Eranikus was corrupted by the Nightmare . Even Ysera ' s most trusted lieutenants ( Lethon , Emeriss , Taerar . and Ysondre ) have been warped by this dark power within the Emerald Dream . Malfurion fights at Cenarius ' side against the Nightmare within the dream , but may have been turned into an Unwaking himself . In The Burning Crusade . The Nightmare seems to have found a way into one of the wings of the Stormrage Barrow Dens where strange creatures of nightmare suddenly come in to the waking world . The Cenarion Dreamwarden are constantly trying to keep the threat at bay . Plant life is thriving here , but this is not the case in the Emerald Dream . Clintar Dreamwalker can be found asleep in one of the rooms and he is part of the quest chain for Swift Flight Form . It seems Anzu is behind these attacks . In Wrath of the Lich King . While on the Icecrown quest , Remulos sends the player into a phased version of a portion of Moonglade to gather . During the Valithria Dreamwalker encounter she opens portals to the Nightmare , where you can find dream clouds . In Cataclysm . The Emerald Nightmare is present in the regrown areas of Southern Barrens . This area is called The Overgrowth and lies just south of the chasm that split the Barrens in the northern west part of the Southern Barrens . In Legion . Xavius and his satyr forces within Val ' sharah are working to bring the Nightmare into the world . Yogg - Saron is the source ? Yogg - Saron is probably responsible for the nightmare corruption in Val ' sharah and possibly the entire Emerald Nightmare . When you enter this region with a shadow priest equipped with , it whispers : " To see Yogg - Saron ' s nightmare in full bloom fills me with jealousy . . . and some pride . "