Thinking again about the Lich King, specifically when Arthas Menethil wore the Helm of Domination, always brings me to speculate on his seeming need to prove something. Everything we experienced in Wrath of the Lich King seemed calculated towards that end. From the encounter with him in Howling Fjord through the complicated Drak'tharon Keep and Zul'Drak storylines to the final showdown atop Icecrown Citadel, Arthas always had a plan, and that plan was in part simply to cause his own enemies to provide him with a cadre of such power that he could turn and use against the world, yes. But more than that, Arthas seemed obsessed with proving that he was right.
Again and again Arthas as the Lich King put mortal heroes through situations that served to illustrate his own fall - again and again, he sought not just to torment and inspire hatred and anger just as he had been tormented by Mal'Ganis and grew to be consumed by hatred, but to show by so doing how his own actions had been correct. That the only possible response to what he'd undergone was to become as he had. Even merged with Ner'zhul in the form of the Lich King, Arthas' mind and personality came to shape the entity, and when all roads converged atop Icecrown, it was Arthas' desire to show Azeroth how right he was that shone through.
The war Arthas started raised Garrosh Hellscream from a hothead with no real position of authority to the head of a Horde war machine that rolled successfully across the frozen north. Make no mistake. It was Northrend that truly showed the Horde its own strength for the first time. The Might of Kalimdor was a joint venture, and the battles across Outland were scattered, a series of excursions rather than a full fledged military campaign. In Northrend, the Horde flexed its muscles for the first time since the Founding of Durotar, and it found itself mighty indeed.
Not only did Garrosh motivate his people to expand across the Borean Tundra, through the Dragonblight and Grizzly Hills, and push north through Icecrown itself but he did so with the kind of brutal efficiency not seen in a Horde leader since Doomhammer. And as he did so, he met the Scourge again and again in battle. While the Wrathgate was a traumatic experience for the Alliance (the loss of Bolvar, the shock of Undercity to King Varian) it simultaneously removed a future rival and taught Hellscream exactly what he would be facing in the upcoming war. The Scourge was a remorseless, pitiless enemy. It did not know fear, it would not negotiate, and so Hellscream employed the only tactics that would be successful against it - total war. You can see the legacy of Hellscream's war in Northrend across Kalimdor today - the seizure of Azshara, the encroachment into Ashenvale and Stonetalon, the push into Gilneas, even the destruction of Theramore are all of a piece with the war that Hellscream learned to fight a war.
It's easy to forget that Hellscream, for all his bluster, had never seriously led anything militarily meaningful before Northrend. This is an orc who spent years gripped by depression and self-loathing, who let Jorin Deadeye do more to lead the Mag'har than he bothered to do himself. When Hellscream came to Orgrimmar. he did so as the untried leader of a clan he'd never seen (the Warsong) whose only leadership experience was in failing to do anything for the Mag'har. Thus, in a very real sense, Hellscream's tutor in war was the Lich King. It was Arthas and his obsession with demonstrating the cost of power that led Hellscream on a merry chase throughout the continent, fighting both the Alliance and the Scourge the whole way.
What did Arthas, the part of Arthas still alive inside the Lich King, want to teach us? Ultimately, that power corrupts. Power corrupted him, and it will corrupt you, too. That it is inescapable, and thus, Arthas couldn't have escaped it - that becoming the Lich King was inevitable, that all kings and princes and people of power ultimately end up slaves to themselves. Not the madness imposed by outside forces. Not Frostmourne or becoming the Lich King - rather, that moment outside Stratholme where Arthas dismissed Uther and Jaina and went on alone to burn and slaughter his own people in order to save them.
So combine the two thoughts - one, Arthas was not the dominant force in the merged Lich King entity, and two, even when Ner'zhul was alone (albeit greatly changed and expanded by Kil'Jaeden) he was not making full use of the Scourge. So we've talked about how Arthas may have influenced Garrosh, but we haven't talked about this: how did Ner'zhul influence him, and everyone else? How much of Arthas' schemes were in fact Arthas at all? How much of it was Ner'zhul?
Remember that encounter with the Lich King in Howling Fjord I mentioned earlier. In it, when the Lich King seizes your spirit form, he specifically states the following.
I find that phrasing very deliberate. Ner'zhul was the shaman, not Arthas. With what we know of Ner'zhul's history - how he instigated the war against the draenei at Kil'jaeden's deception, how he sought to turn his people away once he learned he'd been tricked only to be betrayed by his own student Gul'dan, how he watched powerless to act as the Horde was formed and Grom Hellscream drank the blood of Mannoroth, and how he sought to unite the defeated remnants of Gul'dan's Horde and lead the orcs to a new world - we're left to ask ourselves, how much of what the Lich King taught Garrosh was Arthas' doing, and how much of it was Ner'zhul? Did Ner'zhul make use of Arthas' overweening ego and need to prove himself justified to set a trap, allowing the fallen Prince of Lordaeron to play out his psychodrama while taking each step along the way to teach young Hellscream the lessons he would need to make this world a fitting one for the orcs to dominate, and in so doing, make his own dream of finding a new world for the orcs a reality?
Shamanism has brought you here... Its scent permeates the air. *The Lich King laughs* I was once a shaman.
In the end, the Lich King was Hellscream's greatest teacher. One can act completely of one's own volition, with no magical influences, and corrupt one's own self through the wrong action, learned from the wrong lessons.
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.