Battle of the Crimson Watch

Battle of the Crimson Watch 

At the beginning of the group quest [70] Battle of the Crimson Watch, Illidan shouts out to the players: 
 
Illidan holding the skull of Guldan.
Lord Illidan Stormrage yells: What manner of fool dares stand before Illidan Stormrage? Soldiers, destroy these insects! 

Waves of demons and blood elves attack the party, and the players must defeat the waves, finally battling Torloth the Magnificent. After Torloth falls, Illidan shouts out to the player who landed the killing blow, challenging him to come to the Black Temple and take him on: 
Lord Illidan Stormrage yells: So you have defeated the Crimson Sigil. You now seek to challenge my rule? Not even Arthas could defeat me, yet you dare to even harbor such thoughts? Then I say to you, come! Come ! The Black Temple awaits... 

This suggests Illidan losing his mind over his defeat at Arthas' hand, not believing it himself; on the other hand Illidan did technically survive the encounter, and if "defeat" for Illidan is defined as death, then Arthas did not actually defeat him. Such nuances of logic are common with Illidan, often employed when defending his actions to others. 
Involvement in the Netherwing Quests 

The final quest of the long grind to reach Exalted with the Netherwing is called Lord Illidan Stormrage — it involves speaking with a projection of Illidan himself. Overlord Mor'ghor, leader of the Dragonmaw's nether drake project, presents the player as the new Highlord of the Dragonmaw, but Illidan sees through the illusion and orders the Overlord to kill the player. Yarzill the Merc, a nether dragon disguised as a goblin, helps the player escape to the Lower City of Shattrath where they will receive one of six Netherwing Drakes as their new mount. 
Master of the Black Temple 
Main article: Illidan Stormrage (tactics) 

Agents of both the Alliance and Horde have been assigned to penetrate the Black Temple and eliminate Illidan. Akama and his "associate", Maiev Shadowsong, are covertly involved in the effort. 
Death 

During a quest, it is revealed that Akama has conspired to end Illidan's tyranny by allying with Maiev and later freeing her. In the Black Temple raid encounter, Illidan is the final boss and is fought by both Akama and Maiev along with the players. During the battle, Maiev taunts Illidan several times in reference to the pain that he has caused her, from forcing her to guard his prison for 10,000 years by committing his crimes to causing the death of Naisha. In the end, when Illidan is near death, Maiev remarks that he is beaten, but as he dies Illidan says that the huntress is nothing without the hunted, and by extension that Maiev's life cannot continue. With the drive for vengeance gone, Maiev states that she is indeed nothing, thus making her as much a casualty as Illidan.