The Sunwell Redemption
The final tie between Kael'thas and Quel'thalas was broken when Kael'thas' minions returned to take back by force the naaru, M'uru, which he had once given to his kindred so freely. Lady Liadrin and her Blood Knights would have been left without any of their powers had the naaru A'dal not reached out a hand to save her and her people. Lady Liadrin was deeply regretful of what she and her Blood Knights had done to M'uru, but A'dal forgave them, saying that M'uru had known all along what his role would be in this unfolding drama. The naaru extended his own Light energies to Liadrin and her Blood Knights, and encouraged them to assist him to stop the terrible threat that Kael'thas now represented to all the people of Azeroth and Outland.
The former "Lord of the Blood Elves," now quite insane, had brought the remaining strength of his forces back to Azeroth and taken over the Sunwell Island, just across the channel from Silvermoon City, and planned to use the hidden energies of the Sunwell's magic to try and summon Kil'jaeden into the world. The blood elves and draenei of Shattrath united to overcome this threat, and as their forces ventured deeper and deeper into the Sunwell fortifications Kael'thas had set up, they found that M'uru himself was enslaved as a guard the site where Kil'jaeden would be summoned. The heroes were forced to destroy his weakened body and stop the entropic energies which now began to vacuum up all life around it as the last of his Light energies seemed to drain away.
At last, of course, the heroes faced Kil'jaeden himself at the site of the Sunwell (perhaps your own character was among them), and, with the help of some dragons, they drove him back into the Sunwell Portal, away from Azeroth. The draenei prophet Velen arrived, along with Lady Liadrin, and spoke to the heroes, as he placed the last remaining fragment of M'uru's body into the Sunwell. The result is one of the best scenes in Warcraft lore, which you too can look on, as the last spark of M'uru's life reignites the Sunwell with the energy of the Holy Light, restoring once and for all, that magical life energy the blood elves need, as well as something far greater, something with the power to rebirth the entire civilization of the blood elves: Faith.