The difficulty lie in the fact that Lo'Gosh only had half the story. Upon penetrating into Stormwind (with Marshall Windsor able to convince General Marcus Jonathan to ignore Lady Prestor and allow them entry), the two Varians squared off against one another. They discovered that not only were each equally skilled in combat, but that each of them first thought of the safety of Anduin Wrynn and fought against the black dragon servants of Onyxia to protect him. Confusion heaped upon confusion -- and in the chaotic melee between the two Varians, the black dragonflight, Varian's companions and the Stormwind guard, Marshall Windsor died at Onyxia's claws and Prince Anduin was kidnapped.
Although neither Varian knew what to make of the other, both put their enmity on hold to mount a rescue attempt. Highlord Bolvar Fordragon, who had been Anduin's guardian in the king's absence, found the two Varians to be as different in personality as they were identical in features. Lo'Gosh was brash, direct, and combative to the point of aggression, while the Varian who had been residing in Stormwind for weeks was urbane, diplomatic, even somewhat passive until spurred into action. Together, the two kings of Stormwind made plans to travel to Theramore as a first step in tracking Onyxia to her lair.
Once there, Jaina and Aegwyn, her chamberlain, revealed to the strange twins that neither of them were the true Varian -- or rather, that they both were. Essentially, Onyxia had sought to split the willful, obstinate King Varian in two and then kill the one who ended up with the rage, willpower, and defiance that made her own plans so difficult. The magical ritual used to do this was disrupted by an attacking force of naga. In the confusion, one of the duplicates ended up in the hands of those who would ransom him back to Stormwind; the other escaped Alcaz Island but ended up in Durotar, unable to remember himself.
Thusly, neither Varian could be said to be an impostor, nor could either claim to be the real one over the other. Shaken but still determined to rescue Anduin, they went straight to Onyxia's Lair and confronted the broodmother herself. After a pitched battle (and one in which Anduin showed he was no mere hostage, helping in the attempt), Onyxia attempted to complete the ritual and destroy the Lo'Gosh half of Varian.
However, the supposedly docile diplomatic half of the king did not allow the dragon to strike her target with the spell, throwing himself into its destructive beam before Lo'Gosh, who followed in an attempt to rescue his "brother" -- and so, in a flash of light, the spell did the opposite of the original ritual and fused two kings into one again. Reconciled to himself, the whole King Varian struck Onyxia a fatal blow and ended her shadow reign over his kingdom.
Varian has been an extremely active king since his return. He participated in another attempted peace treaty (this one sabotaged by Cho'gall and his Twilight's Hammer, using Garona as a pawn), although the initial possibilities of this conference ultimately came to naught. While Varian and Thrall managed to find common ground and Varian even offered Thrall a way out of the perennial conflict over resources with the night elves (preparing to offer the Horde all the lumber they needed from Stormwind's vast Elwynn Forest reserves in exchange for copper from Durotar's mines), in the end, the attack using Garona drove a wedge of suspicion between the two factions -- one not aided by Garrosh Hellscream's bellicose presence. It should be noted that the Twilight's Hammer was wise, using the racial tensions of the two factions against each other by having human and other Alliance races among their number be the ones to attack the Horde representatives, and using Garona and other Horde races against Varian and the Alliance.
However, Varian's old friend Arthas had no intention of letting the Twilight's Hammer upstage him. Before the situation could degrade, both Thrall and Varian were forced to return home to their respective capitals, as news had filtered in of new Scourge movements. The news soon became far more than mere reports, as the Lich King struck at almost every major city on the surface of Azeroth with his infamous plague of undeath. Soon, even as armies of the walking dead ravaged the land, the Lich King's voice boomed out over the cities of Orgrimmar and Stormwind, challenging the people of both factions to bring the battle north.
Varian saw no reason to deny Arthas the battle he sought, and soon, the Alliance had begun preparing for war. It even looked for a time as though the Alliance and Horde might well find common cause. Varian had sent his friend and close adviser Highlord Bolvar Fordragon, the man he had trusted with his son's life, north to lead the Alliance effort in the critical Dragonblight.
It could have been one of the greatest moments for peace between the Alliance and the Horde. Instead, it was the death knell for any chance of cooperation between the two. The Horde lost a potential leader in Dranosh Saurfang, but the Alliance lost a proven one in Bolvar Fordragon. Worse, Varian lost a personal friend and saw his son Anduin lose a friend and mentor just as he had lost Anduin Lothar. The parallel did not escape him, and when Varian pursued the mad apothecary Putress into the halls of the Undercity, he came face to face with what the Forsaken had done with the city of his childhood. The subjects in cages, the torture, the deals with demons (Varian had to fight his way through actual armies of demons and undead constructs to make his way to Putress) -- it was every nightmare of the Second War given new life, and it enraged him. After Putress, he heard Thrall's voice, and flew to challenge the orc who had let this go on for years.
Jaina used her magic to prevent the king and the warchief from coming to blows. It's possible that was a mistake. The Wrathgate ended any chance for peace between Alliance and Horde, and following the Horde's attack on Alliance soldiers who were occupied fighting the Scourge, an attack from behind, Varian refused to ally with them in order to prevent the Old God Yogg-Saron's escape from Ulduar. Apothecaries who were members of the Horde had created a death plague and loosed it on his people at the Wrathgate. They had experimented on helpless captives in Undercity, and Horde soliders had attacked Alliance from behind while they struggled against the Scourge.
Throughout the campaign against Arthas, Varian would never again ally with the Horde. The closest he came was in allowing Varok Saurfang to retrieve the body of his son, and that was more a matter of honor between two warriors and a matter of one father understanding another and his grief. The Varian Wrynn who voted not to commit genocide was the same Varian Wrynn who stood atop the Deathbringer's Rise, but older and far more weary.
Before the shattering
Ironically, despite his own protests, Varian would find himself leading an army of dreamers in a battle within the Emerald Dream on behalf of Malfurion Stormrage, and that army contained members of the Horde. Despite Varian's stated antipathy for them and theirs for him, he commanded them well, some going so far as to say they saw the white wolf Lo'Gosh itself impose its features upon his in the dream.
This was not the first sign of Varian's being somewhat conflicted between his dual nature; later events would see him threatening even his close allies in his rage at their constant attempts to make a peace he believes doomed between the Alliance and the Horde. Fearful of his own growing rage, the king decided to send his son to Theramore and then Ironforge to learn various lessons in how to rule, only for the Dark Irons to invade Ironforge while Anduin himself was there.
King Varian led SI:7 operatives to the very mountain itself, finding his son and nearly executing Moira Thaurissan for her action in seizing Ironforge. Anduin, however, once again managed to mitigate Varian's rage. The king helped create the Council of Three Hammers, uniting the Bronzebeard, Wildhammer and Dark Irons in a single ruling body. Since then, the deeply conflicted king of Stormwind has been preparing for war across the world of Azeroth as the effects of the Cataclysm show themselves. Stormwind is right in Deathwing's crosshairs, and it is to Varian that the people will look for protection.
Varian Wrynn is a complicated man, a man at war with himself. As many words as have been expended here in discussing his history could go into a study of his character. For a man who has repeatedly seen those he love come to harm, he is surprisingly tolerant and forgiving. For a man who watched his father die at the hands of someone he trusted, he's remarkably willing to trust. For a man who lost two of his three fathers to orcs, he's given orcs far more of his time and effort than anyone could expect. He once had it in his hands to wipe them off the face of Azeroth, and he chose not to. He met with Thrall for a peace conference after being kidnapped on his way to the previous one.
And yet he is also the man who screamed epithets and threats in the very chambers of the Undercity; the same man who would let an ancient horror loose if he believed it would strike the Horde first; the same man who called the Horde champions of the Crusader's Coliseum animals and savages ... and the same man who let Saurfang claim his son's body; the same man who led Horde and Alliance alike in the Emerald Dream; the same man who ordered his own fleet to avoid the Horde in the face of the threat in the Twilight Highlands.
Ironically, the figure Varian most resembles is Garrosh Hellscream in many ways. Impossible father figures to try and emulate, a sense of destiny always hovering over them, insecurity and doubt, a true desire to protect their people and give them a better tomorrow. Were Varian an orc, they could well be friends.
For more information on the people and places and events mention in this Know Your Lore:
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.