Cenarion Expedition

With no other option, Illidan led the blood elves and naga back to Azeroth. The Scourge kept Illidan's army at bay until Arthas and the crypt lord Anub'arak arrived. Arthas and Illidan faced off in single combat, and Arthas was the victor. He warned Illidan to leave Azeroth and not return.

Since that time, Illidan has returned to thewow gold Temple. While his allies fight to keep Outland's many portals sealed, Illidan is preparing for the day that Kil'jaeden arrives to punish Illidan for failing to destroy the Lich King.As is the case with certain demons, Illidan does not consider himself a servant of the Burning Legion. Indeed, Illidan has alternately been the Legion's ally and its enemy at various points in the past. A rarity among demons, he has retained vast tracts of his original personality despite his demonic transformation. As a demon, he is fundamentally evil and often cruel, but he has thus far been able to preserve a few tattered remnants of nobility. Their inevitable conflict with his ambition and his hunger for power makes him a dangerously unpredictable adversary.

Because Illidan's case is unique, there is no point in speculating upon how long his divergence from standard demonic behavior will last.