He was the last Guardian and one of the most influential people in Azeroth -- but he never meant to be either one. Of all of the myriad and varied heroes in World of Warcraft, there is one man who is responsible for the majority of the events we see in Azeroth today. This man was solely responsible for the presence of orcs, responsible for the Horde, responsible for the ever-evolving conflict between Horde and Alliance. He was responsible for the original destruction of Stormwind, for the death of Anduin Lothar, King Llane Wrynn and many other heroes whose exploits didn't make it into the annals of history. He was responsible, indirectly, for the corruption of Arthas and the subsequent death of King Menethil, the razing of Stratholme and the rise of the Scourge. He arguably has more blood on his hands than any other being in Azeroth.
And yet he was also responsible for the first tenuous threads of peace stretched between Alliance and Horde. He was responsible for the rise of some of Azeroth's greatest heroes -- he was the man that made Varian Wrynn who he is today, he was the man who turned Thrall from an orc with dreams of peace for his people into a leader of action. He was responsible for saving Azeroth from being razed and torn asunder by the Burning Legion. He was a man of many talents, and a man of many regrets. His name is Medivh.
To fully understand Medivh and his odd origins, we have to look at his past. If it weren't for the actions of his mother, Medivh may never have existed at all. Medivh's mother was a woman named Aegwynn with a surprising destiny of her own. Aegwynn was a Guardian -- but what does that mean? What, exactly, is this Council of Tirisfal we keep talking about, why was it founded and how did it come into play? For this, we need to look into Azeroth's history and the history of the leader of the Burning Legion, Sargeras.
The resulting War of the Ancients is well documented. Malfurion Stormrage, along with several others, managed to stop Sargeras' advance into Azeroth and banish him back to the Twisting Nether. But Sargeras never forgot the little world with the magical well, even though the well itself was destroyed and Azeroth torn apart by the Sundering as a result of the well's destruction. The elves were split into two distinct factions -- those that were one with nature and hid in darkness, and the higher-ranking elves, former nobles who longed for the days in which they could use the arcane. But they were forbidden to do so upon penalty of death -- Malfurion and the other kaldorei recognized the dangers in meddling with the arcane arts and did not wish to see a repeat of the War of the Ancients.
Some of these high elves finally rebelled and found themselves banished as a result of their actions. After setting sail across the oceans, they discovered the continent of the Eastern Kingdoms, landing in what is now called Tirisfal and settling there for a time before moving north to what we now call Quel'thalas. Here they founded the Sunwell, a font of magical energy that was a weak mockery of what the Well of Eternity had been -- but that still served the purpose of the quel'dorei. The elves fought with the trolls who already inhabited the area, and once again, the elves found themselves in the middle of a war. But this time, they had allies in the small and primitive human race. In exchange for the humans' help, the quel'dorei agreed to teach 100 humans the art of arcane magic.
There was a problem, however, with concentrating all magical power and practice in one location -- something that was a familiar problem to the quel'dorei. The high concentration of magic, combined with that powerful ley line, attracted the attention of the Burning Legion. Demons slipped through dimensional gaps, ravaging the city and terrifying its citizens. The problem grew large enough that the human mages sought out the high elves' aid. The quel'dorei recognized the issue. They told the humans that in order to neutralize the threat, they would have to give up practicing the arcane arts they so loved.
But with power also comes the desire to wield it, and the humans were unwilling to give up that power. Instead, they suggested an alternative: to select a mortal champion who would be responsible for protecting the city and all of Azeroth from the Burning Legion's watchful eye. This "spearhead" would be imbued with the magic of the most powerful mages, and the mages who lent their power to the spearhead would form a council. The elves agreed to this, and together, these powerful mages formed the Order of Tirisfal, also called the Council of Tirisfal or the Tirisfalen.
Right. That makes loads of sense.
Regardless, the Council of Tirisfal worked against the demons to some effect, but a problem arose fairly quickly. While the mages of the Council could lend their power to the spearhead, they had to be nearby, which put their lives at risk, because their powers were all lent to the spearhead they'd chosen. After some time, Alodi, a half-elven mage, devised a spell that would allow the mages of the Council to transfer their powers over great distances, allowing the spearhead to act without putting the Council in harm's way. He also suggested a change: Rather than a "spearhead," the name of the chosen one would be Guardian, a protector who would watch over not only Azeroth but also the Council of Tirisfal. The way the spell worked was fairly simple: Each mage on the Council had a lot of magical power. Through the ritual, part of their powers would be channeled into the Guardian, and the Guardian would use their power to fight the Burning Legion.
The Council of Tirisfal was a secret order; very few knew of its existence or of the existence of the Guardian. But the Guardian and the Council always kept a watchful eye out for any promising new mages who could make a potential new Guardian. Nearly 850 years before the events in World of Warcraft, the Council's chosen Guardian was a mage named Scavell. Magna Scavell had several apprentices that he was training to take over for him when his time as Guardian would eventually pass. Although all five of his chosen apprentices were promising, only one showed remarkable potential, a girl named Aegwynn. Though she was often mocked by her classmates and told that "girls couldn't be great wizards," it was Aegwynn who was chosen to become the next Guardian.
Aegwynn was given the powers of the Council and quickly set to work. The first of many demons the fought was named Zmodlor, who was possessing children in a schoolhouse near Dalaran. Aegwynn got rid of the demon before the children were harmed, but the Council had words with her in regards to her rush to get rid of the demon -- she destroyed Zmodlor before anyone could determine why the demon was there or what his ultimate plans were. Aegwynn rankled under the criticism, arguing that she couldn't let children suffer simply because the Council wanted to observe. Thus began a long and rocky relationship between Aegwynn and the Council.
After burning the demons to a crisp with the help of the dragons, Aegwynn was confronted by none other than Sargeras, leader of the Burning Legion (or rather, an avatar of Sargeras). The Guardian and the Dark Titan fought furiously, but Aegwynn prevailed with the help of the dragons and destroyed Sargeras' avatar. She took what was left of his physical form to a place now called the Tomb of Sargeras and buried it deep below the earth where none could find it. But the fight and the victory got to Aegwynn in a way that none of her previous battles had. She'd fought and defeated the leader of the Burning Legion, on her own, with no Council to help her. She'd done what was thought impossible -- so why was she listening to the Council at all?
Indeed, why should the Council of Tirisfal choose the next Guardian, when she possessed greater judgment and finesse than the lot of them combined? These thoughts haunted her for the next several hundred years, until at last she realized that despite the use of magic to extend her lifetime almost impossibly long, she was still mortal and would not last forever. But the Council's meddling had become unbearable to the arrogant Guardian, and she decided that she would choose her successor in a way that nobody on the Council had anticipated: by giving birth to him.
Aegwynn traveled to Stormwind, where she seduced the court conjurer Nielas Aran. There were two factors in her choice, and neither were love. Nielas was a practiced and powerful magician in his own right; therefore, the child he fathered would posses the same affinity for magic as his father -- and more importantly, Nielas was nowhere near Dalaran, the Kirin Tor or the Council of Tirisfal, so the child could be raised far, far from the Council's prying influence. While Nielas was initially delighted that Aegwynn appeared to have fallen in love with him, he was soon disappointed to find the opposite was true -- that he was just a means to an end, that end being Aegwynn's son.