Where others may have quailed from the looming threat of darkness, they embraced it. Where others reviled the blatant corruption of the Burning Legion, they not only accepted it, they went looking for more. And where others may have listened to common sense and turned from the face of evil, they saw evil for what it was, took its measure and took what it had to give, gladly. It wasn't about corruption, it was never about corruption -- it was about power.
And for the Shadow Council, power was everything.
Formed long before the creation of the Dark Portal and the first invasion of Azeroth, the Shadow Council managed to survive the death of its leader. In fact, it thrived in his absence, and despite the supposed extermination of this dark society, it still thrives today, albeit in lesser numbers than before. But though its direction and leaders may have altered, its purpose has never really changed -- devotion to the Legion, at whatever costs that may entail.
Long before the Horde crashed through the Dark Portal and brought about the First War, the orc race was merely a collection of clans. Ner'zhul, shaman of the Shadowmoon clan, served as a spiritual leader for all orc clans. It was the closest thing they had to a Warchief at the time. Ner'zhul's apprentice was Gul'dan, and although Gul'dan showed extraordinary proficiency with shamanism, he was not liked. He was not really trusted. As Orgrim Doomhammer said in Rise of the Horde, "I think that Gul'dan would better serve his people if he were set out as bait."
Ner'zhul eventually fell under the sway of Kil'jaeden, who quietly managed to convince Ner'zhul, and through him, the rest of the orcish race, that the draenei were planning to wipe them out. And while all this was happening, Gul'dan observed, and observed well the power that Kil'jaeden offered. It was little surprise, then, that Gul'dan betrayed Ner'zhul, trading in his former master for a chance to stand at Kil'jaeden's side, prove his loyalty, and be rewarded with all the power he could ever hope to obtain.
But where Ner'zhul had been a spiritual leader, someone that held the respect of all clans, Gul'dan did not. There was no way that Gul'dan could hope to control the orc clans the way that Ner'zhul had. It was to this end that he formed a secret cabal of those who had eagerly embraced Kil'jaeden's dark teachings -- warlocks -- and used this secret society to quietly manipulate the clans from within. This group was called the Shadow Council, and few knew of its existence, although there were fewer still that weren't touched or influenced by the Council in one way or another.
Obviously Gul'dan couldn't just let the clans remain leaderless, and so he took under his wing Blackhand, the leader of the Blackrock clan. Blackhand was strong, and if not beloved, at least respected by his fellow orcs. Gul'dan saw in Blackhand an orc that could be the potential leader of the united clans -- one who could also be easily manipulated, if the right words were said. Gul'dan may not have been particularly liked, but he had a way with words. Through flattery and trickery that likely made Kil'jaeden proud, Gul'dan told Blackhand of his plan to unite the orc races into the Horde. He offered Blackhand a place on the Shadow Council, and that position of leadership.
And then Gul'dan went to the orc clans and held a public vote for the position of Warchief -- one that Blackhand handily won, largely due to Shadow Council members quietly influencing their individual clan leaders into voting for him. Blackhand played his role exactly as Gul'dan intended. He never had any real influence in the Shadow Council, and he never really had any real influence over the Horde -- he was simply a puppet that Gul'dan easily tricked into doing his bidding, time and again. The Shadow Council continued their work unopposed.
That work was essentially the corruption of the orcish race. The warlocks of the Shadow Council were former shaman who had lost their connection to the elements. Frustrated and devoid of power, they were happy to take that power when it was offered, happier still when they were told that they would be the masters of that power. No more did they need to wait on the whim of the elements -- they could simply order their minions to do their bidding, use demonic powers to destroy.
Blood of Mannoroth
The Shadow Council continued to do the bidding of Gul'dan throughout the First War. There was no end to their depravity, no depth to which they would not sink in exchange for more power. They prematurely aged the children of the orc clans to provide more soldiers on the battlefield, manipulated their clan leaders into doing whatever Gul'dan, and through him Kil'jaeden, wished to see done. They fanned the embers of aggression into all out war, tended the flame and made sure that above all else, the draenei race would be wiped out.
And when at last the orcish race had destroyed most of the draenei settlements on Draenor, Gul'dan and the Shadow Council had a reward for the orc clans -- the blood of the great pit lord, Mannoroth. Drinking his blood granted increased strength, aggression, an unquenchable bloodlust. It also resulted in almost complete and total corruption, but it was little price to pay for the power. Shattrath was destroyed by demon-fueled hands, and the orcs moved on to Azeroth -- Gul'dan offered even more power in exchange for the relocation of the Horde, this time from Medivh.
And in the end, that was Gul'dan's downfall, really. Both he and the Shadow Council grew far too arrogant. When push came to shove and Gul'dan sensed Medivh's imminent demise, he tried to pluck the location of that reward he'd been promised from Medivh's head -- just as Medivh was beheaded. Gul'dan fell into a coma, and Orgrim Doomhammer, who had been observing everything that was done during the First War, took that moment to strike. He killed Blackhand, assumed leadership of the Horde, and systematically murdered the majority of the Shadow Council, theoretically ending their influence.
But it really wasn't that simple. Certainly Doomhammer let Gul'dan live, after he'd awoken from his coma. He even let Gul'dan create the first death knights, let him lead his warlocks alongside the Horde in the Second War. It was a foolish move, one that Orgrim would regret when Gul'dan decided to cut his losses and seek that reward Medivh had promised him long ago, deserting the Horde in the process. Gul'dan was killed in the depths of the Tomb of Sargeras, and supposedly, the rest of the Shadow Council died with him.
Yet the Shadow Council still exists today. They do not have a Horde to manipulate, and their members have grown in size. Although the organization is still primarily comprised of orcs, other races have joined the ranks of the Shadow Council. The Council no longer exists solely to manipulate a race into open warfare -- instead, they simply practice their dark magic and work tirelessly at their ultimate purpose: carrying out the will of the Burning Legion.
In a way, the Council far outgrew its original master. In another way, Gul'dan couldn't really be called the Council's master at all. If there was one thing Gul'dan should have realized, in his careful manipulations of the Horde and his puppetry of Blackhand, it was that he was also merely a puppet for Kil'jaeden. No mortal race, no organization of individuals can dare call themselves masters of the Burning Legion -- merely its servants. There is no controlling the Legion, merely using its powers and paying the price for the privilege of doing so. But for the members of the Shadow Council, both then and now, the promise of power, the semblance of control, and the dark thrill of corruption is more than enough to warrant the costs.
While you don't need to have played the previous Warcraft games to enjoy World of Warcraft, a little history goes a long way toward making the game a lot more fun. Dig into even more of the lore and history behind the World of Warcraft in WoW Insider's Guide to Warcraft Lore.