"Foolish little mongrel! You failed to destroy the Frozen Throne as I commanded, and still you thought to hide from me in this forsaken backwater! I thought you to be more cunning."
Race: Eredar
Occupation: Head of the Burning Legion
Alignment: Burning Legion
First in the ranks of the Eredar, the demon lord Kil’jaeden is as vile as he is powerful. Selected by Sargeras as his champion, Kil'jaeden was responsible for the enslavement of the Dreadlords to the will of the fallen Titan, and their leader, Tichondrius, vowed to follow Kil'jaeden's dark agenda of assimilating every race possible into the folds of the Burning Legion. The Legion's malefic swallowed world after world, leaving nothing but fire and destruction in their wake. Though Archimonde was given much credit, the Legion would never had done it had Kil'jaeden not done his job so neferiously well.
Kil'Jaeden never invades worlds directly; rather, he and the Dreadlords eat away at the world slowly corrupting it from within. Though much slower (and less satisfying to most demons) than Archimonde's favored method, it is chillingly effective nontheless.
Kil'jaeden soon found a power of great potential: the Orcish Horde. How he located the orcs is essentially a mystery. Some say he located them by accident, but the dragons Alextrasza, Nozdormu and Korialstrasz suspect that Kil'jaeden began searching for the orcs after Broxigar injured Sargeras at the final battle in the War of the Ancients.
Going straight to the Horde's most respected leader, Kil'jaeden promised the elder shaman, Ner'zhul, power and longevity that rivaled the Titans themselves if he vowed the orcs to Kil'jaeden's will. Ner'zhul quickly accepted.
However, soon it became apparent that Ner'zhul lacked the ambition and defiance to successfully carry out these plans, and Ner'zhul, beginning to realize what the pact would do to the Horde, refused Kil'jaeden any assistance, and so Kil'jaeden turned to a budding orc, whose practices in dark sorcery had begun already: The warlock known as Gul'dan.
Gul'dan's indomitable lust for power and his selfish disregard of anything but himself made him the perfect pawn for the demon. Mannoroth's blood was given to the orc chieftains, and they degraded into a bloodlust that destroyed the Draenei.
Kil’jaeden, like the rest of the Eredar warlocks, felt the power of Medivh when he began his astral roaming, but his power was rife with the scent of Tirisfal, and this frightened the demon to no end (or not- we have only Gul'dan's testimony to suggest that Kil'jaeden was frightened of Medivh, and it is possible that the Deciever recognized Sargeras deep in the Guardian's thoughts). His agendas were fulfilled as the Horde made their way into Azeroth, spreading their dark, demonic energies wherever they went. They heralded the destruction that would wipe out any resistance that could be offered to defend against the Legion. However, they fell in the Second War. As if that wasn’t enough, a young, revolutionary orc named Thrall began to re-examine the shamanistic traditions of his ancestors, making the demonic presence in Azeroth a minimum. The orcs had failed.
Kil’jaeden knew that the time had come to take matters into his own hands. He found Ner’zhul within the Twisting Nether, and, anxious for vengeance against the shaman's defiance, tortured the orc for an impossibly long time, destroying his body piece by piece until finally, nothing remained but the shaman's tortured soul. Kil'jaeden transformed that spirit into the Lich King. They were to succeed where the orcs had failed, they would wipe out any potential resistance, and raise the unfortunate spirits as undead legions. The Scourge was just that, and wiped out Quel'Thalas and much of Lordaeron before Archimonde first arrived.
However, the Lich King betrayed the Legion by facilitating the death of Tichondrius, and by extension the fall of Archimonde.
Kil'jaeden then went about to acquire a new pawn. He found Illidan, and told him that, despite his part in the Legion's downfall, Kil'jaeden was willing to offer him one last chance at power. He told him that if he destroyed the Frozen Throne, thus killing the Lich King, that Kil'jaeden would reward him with everything he's ever hoped for.
But Illidan failed to destroy Icecrown, and fled to Outland, defeating Magtheridon and destroying the dimensional gates to keep Kil'jaeden and his minions out. But Kil'jaeden already had a presence there, and so appeared to Illidan and commanded him to return to Northrend to finish what he started, and that if he failed again, Kil'jaeden would hunt him down, and he would have nowhere to run.
Now, however, Illidan failed, and the Lich King persists. However, Kil'jaeden, being an ever-scheming Eredar, likely had another plan in waiting. He rarely appears to personally take part in battles and is looked at as cowardly by those foolish enough to doubt his power. He is said the be more powerful than even Archimonde and has an extremely devious and intellegent mind rivaling that of Sargeras himself.
With Sargeras missing and Archimonde dead, Kil'Jaeden, as the single most powerful demon in the universe, has probably taken complete control of the Legion.
