In the Twisting Nether, after Gul'dan was torn to shreds, Sargeras simply left behind an order to continue the invasion of Azeroth and departed. He needed to hibernate to recover his strength.
Azeroth itself was a slumbering Titan-soul. The time it would take to awaken was unknown, but its potential was the strongest among all known Titans, far stronger even then Sargeras. This potential both terrified Sargeras and solidified his resolve. He would either enslave it or destroy it completely; he would absolutely not allow such a threat to exist.
Kil'jaeden was responsible for planning the operation, while Archimonde was in charge of its execution. One was the fist, the other the mind.
"You're in charge. I have other matters to attend to," Archimonde said before leaving directly. He had no interest in even inquiring about these plans.
Kil'jaeden's face fell. He understood perfectly well why Sargeras had partnered him with Archimonde: it was for checks and balances, to prevent the Burning Legion from becoming his one-man show. His gaze fell upon the brilliant river of stars in the astrolabe, and he fixed his eyes on Draenor. This time, he had to come up with another brilliant plan.
Just then, a dreadlord approached. "Honored Deceiver, we have found this block of extreme frost in the depths of the Twisting Nether. This object seems to possess an incredible power; it can amplify psychic energy by tens, or even hundreds, of times. I found this item to be miraculous, and so I present it to you."
Kil'jaeden was preoccupied with plans for the subsequent invasion of Azeroth and was in no mood to look at some treasure. He was about to toss it aside when he looked at the block of ice. His fel-energy-flickering eyes darted about as an idea seemed to strike him.
"Go contact those orcs on Draenor. Find a warlock skilled in fel magic and help him grow in power. I have arrangements for him."
"Yes, honored Deceiver. I shall see to it at once." The dreadlord humbly withdrew, but inwardly, he was laughing at Kil'jaeden for being an idiot. In the presence of a dreadlord, any scheme was useless. They were the most intelligent race! Long live Sire Denathrius!
A good leader is always adept at learning from failure, and Kil'jaeden was no exception. After reviewing the entire process of the Horde's invasion of Azeroth, he didn't pay the so-called humans any mind. He just felt that the orcs were still lacking something. The failure of this invasion was due not only to the betrayal of his lackey, Gul'dan, but also to internal conflict within the Horde! This conflict prevented the Horde from exerting its full strength. Therefore, for the next attack on Azeroth, he would forge a puppet army that would never defy his commands. That way, betrayal would never happen again!
Kil'jaeden grew excited at the thought. He had recently been conducting experiments on the power of death and had discovered that puppets resurrected with this power were quite effective. Although they were a bit weaker, their strength lay in their simplicity and vast numbers. Plus, with the wills of the dead held firmly in his grasp, they would never betray him!
However, a new problem soon arose. Who should be given control of such an army? The dreadlords? Those big bats were a bit too cunning. Although their strength was negligible in Kil'jaeden's eyes, he still had to be careful. Searching through all the demons under his command, Kil'jaeden found no suitable candidates. First, the candidate had to be able to enter Azeroth. Second, their power had to be relatively weak, but their psychic strength relatively strong. Lastly came loyalty and the ability to execute orders.
After much thought, Kil'jaeden still had no clear ideas. He decided to first focus on creating the so-called undead puppet army and then look for a suitable commander.
Eastern Kingdoms.
At this time, Orgrim had led his army to rendezvous with the forces from the Hinterlands and had received some good news. Several more clans had arrived from Draenor, bolstering the Horde's combat strength. The Warsong and Shattered Hand clans, which should have remained behind, had also arrived early. The Warsong chieftain, Hellscream, was a fierce warrior capable of cleaving a demon lord commander in two, while the Shattered Hand clan had already surrendered to Arthas.
This meant that Draenor was almost completely undefended and empty. If the Alliance were to invade Draenor, the orcs there would likely be as helpless as lambs, with no power to resist.
After joining the main force, Orgrim consolidated his troops and began a gradual retreat. His plan was to fall back to the vicinity of the Dark Portal, abandoning the territories they had already conquered. This would allow the Alliance to grow complacent over territorial disputes, and eventually fight amongst themselves, buying the Horde some precious breathing room.
Faced with an already certain defeat, Orgrim did not give up. He was still trying to find a way to keep the Horde functioning. If they failed again, the orcs would be doomed for all eternity. The trajectory of history had already deviated significantly. The Warsong and Shattered Hand clans, which should not have appeared, had shown up, and two other clans had surrendered. Coupled with the empty state of Draenor's forces, there was no way to organize a second invasion.
Sir Lothar led the Alliance army in continued pursuit, wanting to drive the orcs back to Draenor in one fell swoop. But then a letter from Arthas arrived in his hands. After reading it, he fell silent. He began to summon everyone for a meeting and informed the other kings of the situation.
"Another new threat?"
"Another orc invasion?"
"Are you kidding me? This massive war has already pushed my treasury to its limits, and now we have to keep fighting?"
Every king was struck speechless with astonishment upon reading the letter. This was a war they absolutely did not want to fight. Because the enemy was too poor! Even if they defeated the Horde, there was little profit to be squeezed from the orcs, certainly not enough to cover their losses. As for orc slaves? One look at those bloodthirsty orcs, who would seize any chance to crazily bite their guards to death even as captives, was enough. This had led the Alliance to take almost no prisoners, killing them all.
War often meant wealth. If it could lead to an increase in wealth, then absolutely no one would object. But now, this was a completely loss-making venture that no one was willing to undertake.
Arthas's letter stated that a race of insectoids had appeared on the continent of Kalimdor and was rampaging, devouring the land. If left unchecked, it would lead to the fall of Kalimdor. If these creatures encountered strong resistance and then collaborated with the monsters of the sea, they might cross the ocean to wage war, and the human kingdoms would face a new round of threats.