Illidan had sunk deep into the depths of his mind. He had not noticed what he has lost until it was returned to him; he had ripped his souls back from the vile rune blade, Frostmourne. Now his mind was filled with anguish and exultation.
To be whole once more was a feeling he could not describe without words, it felt like he had been living, but without any of his senses to enjoy life, and now that it was returned to him he was complete once more, however the past now caused him great pain when he remembered what he had done.
He knew he had never seen good or evil when it came to power, but he had never sought to become a vampire, sucking their magic's from them, too fuel his own. Now the very idea of what he had done repulsed him, and he once more cursed the Lich King for scar he had put on his life. The greatest pain came not from his actions, but that he would not get the chance to right the wrong he had done.
He knew his body was dying, he could feel it as clearly as he could feel the beating of his heart. He had exercised his body of the demonic power that had become a part of him for so long, his fiery eyes, his tattoos, and the demonic energies of the Skull of Gul'dan; all these he had unleashed upon the Lich King, to buy him time, so that he could infiltrate Frostmourne and liberate his soul from its embrace.
The damage to his body and the shock it sustained from having all of that demonic influence ripped from it in an instant was too much for it, and he could feel his life slowly ebbing.
The time he spent within Frostmourne had seemed like an age, the rune blade had forced him to relive all of his failings and the harm he had caused others. He would have been overcome with the grief of that which he had faced if not for the soul trapped within the sword like his, Arthas Menethil. His childlike soul still lived on within the rune blade, and all that time it was faced with hell itself, Frostmourne was unable to kill off the soul, but it's eternal hunger still sought it, and every waking moment that one pure soul ran from an endless torment, until it found Illidan and showed him how to cope with the horrors Frostmourne would unleash upon him.
That soul had told Illidan the truth of the fate that had befallen the prince, and why the Lich King had not risen up all the dead of this world and unleashed them upon the living. Arthas' need to save his people had led him to his ultimate fate, but it was more than simple him losing his soul, and turning on his people. Arthas had been faced with the damnation he had cast upon his people, and faced with that monstrous act it was easier for him to blind himself from what he had done and become a mindless minion to the Lich King, more so now that Frostmourne had taken his soul from him. So he had submitted to Ner'zhul, the being known as the Lich King, but subconsciously his mind still fought the evil, even if he himself was not aware of it, and so when Arthas put the Lich King's crown upon his head the fusion was not complete, and Arthas' mind still now battles with the Lich King, and while the Lich King has all but subdued him, he has managed to stay the Lich King's hand, even after the Lich King had torn out Arthas' heart, and hidden it from his body to further twist his mind to his will.
The child like boy, that was Arthas' soul had told Illidan the only path to redemption for the fallen prince, for if his soul and heart were reunited, and the being known as Ner'zhul were defeated, Arthas may yet once more return to his people, for his body is not dead, the Lich King was nothing but a parasite, and he needed a living vessel to walk upon this earth, and it was Arthas he had chosen, and to make him obedient he took from him his soul and heart, but he could not take his mind, and it is that one glimmer of light that still holds the Lich King's wrath from consuming this world.
For all this to be done the boy warned Illidan however, a pure form of light must be found, to purify Arthas' heart before it was placed within his body once more, for the Lich King had cast unholy spelled around the heart, turning it into a void. If it was returned to its rightful place as it were it would destroy Arthas' body utterly.
Even if it cost Illidan his last breath he would have this truth known to the world, he would tell Maiev what must be done. She would need a new path to follow, for he had felt her vengeance and he knew it would not die with him, and if left without purpose it would only serve to harm their people. He had denied her vengeance against him, but maybe he could pass it onto the Lich King. He knew she would stop until she finished her task or death took her. But first he must was more return to the waking world.
As Illidan's mind once more returned to his body the pain of its purification engulfed him, soul and all, but still a smile spread upon his face, he knew this was the price of having his soul returned to him and he welcomed it.
His smile was soon replaced by his grim determination to have his last words spoken.
'Maiev,' he called. He could sense her close to him. 'Thank you, your vengeance gave me the strength to overcome my grief. To think it was this that hunted me, I am glad I never had to face it fully.'
'Illidan…' She said. Her voice was unusually hesitant.
'Do not fear Maiev, the bond that tethered us together was broken the moment I regained my soul.' A chuckle escaped Illidan; the thought of having attached himself to her soul was ludicrous to him now.
'I must tell you of the true threat that surrounds our world.' He warned, and told her the truth of Arthas Menethil and the Lich King.
His breath was coming in short gasps now, he could feel his body slowly starting to shut down, and he knew this time was short.
'Remember, Frostmourne must be destroyed for the souls to be… free.' He breathed. 'His heart… fallen to darkness… the Naaru… the spark… it will save it… save him…'
Illidan lay there on the ground. He listened to his breathing grow shallower, and the sounds of the Moon Glade filled his ears. He wished that he could once more look upon the beauty of the forest. He saw only darkness now, and that small spot of light, he moved toward it, and it grew larger, until it replaced the darkness inside. Illidan let his last breath leave his lungs, and he passed into the light, knowing he had shown his people the way at the end.