The World of Warcraft is an expansive universe. You're playing the game, you're fighting the bosses, you know the how -- but do you know the why? Each week, Matthew Rossi and Anne Stickney make sure you Know Your Lore by covering the history of the story behind World of Warcraft.
While Sylvanas was eliminating anyone who challenged her dominion over what was left of Lordaeron (stealing the only thing that she could of Arthas' in the process), Menethil, self-proclaimed king of Lordaeron, was making his way north. After having fought his way past Bloodfeast, surviving Sylvanas' ambush (thanks to the lich Kel'Thuzad) and traveling for weeks, Arthas made landfall in Northrend. His master's voice commanded him to return, and Arthas could not defy it, since his very soul had been taken from him by the runeblade Frostmourne he wielded as a death knight.
So came Arthas again to Northrend, the last time he would travel there -- and, until the creation of Acherus and the new death knight order, the last time he would leave.
With the Frozen Throne itself breached and Ner'zhul's prison falling apart, the spirit of the former shaman knew he had no choice: Illidan's initial attack had severely weakened him, and there was no chance that Kil'jaeden would let an opportunity to punish Ner'zhul's latest treachery pass him by. Having already suffered the agony of being torn apart entirely and encased as a bodiless spirit inside the eldritch armor of the Lich King, Ner'zhul was not eager to see what Kil'jaeden had in store for him this time.
When Arthas made landfall in Northrend, he quickly found himself under attack. A force of blood elves led by Kael'thas might well have made short work of the death knight. Kael'thas' reforged runeblade Felo'melorn now possessed power sufficient to turn away the strikes of Frostmourne, leaving a weakened Arthas unable to secure his usual means of victory. Luckily for him, the Lich King had sent another minion to make contact. Anub'arak, the Crypt Lord, saved Arthas from the blood elf ambush, although Kael'thas escaped.
Anub'arak had once been the king of the vast Nerubian civilization before dying to the Lich King's forces. This invasion, called the War of the Spider, was a near victory for the Nerubians, but their civilization could not endure the deliberate use of their own dead against them. In death, Anub'arak was forced by the Lich King to cull his own people. As the Crypt Lord once put it to the then-living Kel'Thizad, "Agreed implies choice." Anub'arak had none.
The Traitor Kings
Anub'arak and Arthas quickly saw that Kael'thas and Vashj had arrayed large forces in Northrend, and it would take too long to fight their way through them. If they were to reach the Frozen Throne in time to save it from Illidan, they would need to outmaneuver his armies. Anub'arak suggested that they use the subterranean kingdom of Azjol-Nerub, his former home, to effectively go around Illidan's forces, and that they make a slight detour first to kill the ancient blue dragon Sapphiron. This wasn't due to some irrational hatred for blue dragons, but rather because the ancient wyrm was one of Malygos' appointed guardians of a vast magical trove. With the dragon slain, Arthas and Anub'arak could make use of his hoard themselves.
Arthas, aware that Anub'arak knew the terrain far better than he did, accepted both ideas. The battle with Sapphiron was far from easy, but in the end, the real treasure of that victory wasn't the magical artifacts they stole; it was Sapphiron himself. Slain in pitched battle with the two kings, Sapphiron was recreated by Arthas as a frost wyrm, using much of the death knight's waning necromantic power. The investment paid off. Using Sapphiron as an unliving weapon, Arthas cleared Illidan's forces out of the way of the entrance to Azjol-Nerub and then was also used to slay the remnant of Muradin's old expedition led by Bael'gun Flamebeard. With these distractions wiped out by the frost wyrm, Arthas and Anub'arak could delve into the depths of the Inner Kingdom.
The endless darkness
The two kings had fought their way through many of Anub'arak's old subjects, now turned against him due to his slavery at the Lich King's hands, and before his death, Bael'gun had warned that an ancient evil lurked in the depths of the Inner Kingdom. Now Arthas would see that evil firsthand.
At first, he and Anub'arak were forced to do battle with the Faceless Ones, tentacled aberrations that were legendary horrors to Anub'arak's people. Then, however, they found themselves locked in battle with a far more terrible foe, The Forgotten One. This ancient horror was so terrible even the Nerublians viewed it as a creature to be avoided, and both Arthas and Anub'arak were forced to do battle with an army of faceless ones just to reach it, only to discover that by itself it could spawn a nearly inexhaustible stream of horrors to fight them.
They managed to overcome the abominable entity and make their escape, only for Arthas to lose the support of Anub'arak. A collapsing tunnel left Arthas alone to make his way through the cunning traps of the spider kingdom until Anub'arak finally managed to dig his way to Arthas, somewhat surprised and impressed to find the death knight relatively unscathed. The two made their way to the surface.
Kings and pawns
The final confrontation with Illidan's forces was now under way. As Arthas reached the surface, Ner'zhul contacted him directly, explaining that Illidan was already laying siege to the Frozen Throne itself. In order to reach the Lich King, Arthas would need to find and activate four obelisks that surrounded it while also doing battle with Illidan's forces. Ner'zhul used the last of his waning power to invest Arthas with as much of his former might as possible, warning his most loyal servant that this battle could not be lost.
Arthas and Anub'arak fought their way through Illidan's forces, the crypt lord protecting the death knight as he activated each in turn. Finally, Arthas made his way to the entrance to the Frozen Throne itself, where Illidan waited for him.
When they'd first met, Arthas had pronounced Illidan and himself to be a near match. The battle that followed proved it so. Illidan fought out of fear of Kil'jaeden's punishment, however, while Arthas was motivated by the burning voice of Ner'zhul that had replaced and stolen his very soul from him. Despite Illidan's thousands of years of experience, in the end Arthas managed to force and exploit an opening in the former night elf's defenses and struck him down with Frostmourne.
As soon as Illidan was no longer an obstacle, Arthas made his way up the long staircase that led to the Frozen Throne itself, and the icy prison that held Ner'zhul's spirit, dogged all the way by the voices of those he'd once held dear. They failed to save him.
What happened next has been discussed in great detail already. Arthas and Ner'zhul would sit atop that pinnacle for five years, and the world would move on waiting for them.
Next week, Rexxar. 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.