The Brotherhood of the Horse did not lack manpower. The problem was that Stormwind Kingdom was currently short on griffins.
Only dwarves could tame fierce beasts like griffins; it was practically a racial talent. Most wild griffins lived in the Hinterlands, and the Wildhammer Dwarves living there had no real relationship with Stormwind City, so the number of griffins was very limited.
Scraping them together under urgent circumstances, Windsor had managed to find around fifty.
Lothar knew this as well, so he selected only a few elites to accompany him and settle the score with the demon parasitizing Medivh's body.
He had not intended to bring Khadgar, because he was too weak, but the apprentice strongly insisted on coming along.
Since the party did need a Mage, especially one familiar with Sargeras's habits, Lothar assigned Khadgar a griffin after all.
Lothar still did not believe Deathstroke was a Mage. No matter how he looked at him, he simply did not seem like one.
Guided by Deathstroke, the group headed for what would one day become the Blasted Lands—today's Dark Swamp.
Since the Timeline had changed, Sargeras was no longer hiding in Karazhan's secret chamber, nor did he plan to fight everyone to the death in the Mage Tower. There was one thing he had to do: open the Dark Portal for the orcs.
Especially after Deathstroke had stopped the Burning Legion demons' warp jump, the only army Sargeras could use in the short term was the bloodthirsty orcs.
The Dark Portal on Azeroth's side had been secretly built deep within the Dark Swamp under his control of Medivh. Not to mention it had undergone a full three years of test runs and adjustments, such a massive stone gate and its many Magic Circles could not simply be abandoned.
Su Ming