Sylvanas makes a temporary alliance with Garithos against the dreadlords

Full History

Sylvanas formed a temporary alliance with Garithos and his surviving human forces against Balnazzar's control of Lordaeron's capital. The arrangement brought former enemies together for one immediate objective: removing a dreadlord from the ruined city. Neither side entered the coalition with the same vision for the kingdom's future.

Garithos commanded remnants of the human military order left behind by the Scourge's destruction. Sylvanas led undead who had escaped the Lich King's power and were seeking a territory of their own. They distrusted one another, but Balnazzar stood in their way. Cooperation made it possible to defeat a stronger enemy without resolving the question of who would rule once the fighting ended. The seeds of betrayal were therefore present from the beginning.

After the capital fell, Sylvanas ordered Varimathras to kill Garithos and retained control for the Forsaken. The episode explains the rise of Undercity as more than a simple liberation from the Scourge. It emerged from shifting alliances and violence among the powers competing to inherit a ruined human kingdom.