Corp'rethar: The Horror Gate

Corp'rethar: The Horror Gate is the last line of defense used by the Scourge. Its gate and walls are made almost entirely of saronite, near indestructible, and manned by massive Scourge constructs. Behind this gate lies the infamous Icecrown Citadel, the seat of power for the Lich King.

As the sole way for any kind of force to invade Icecrown Citadel would be to breach these gates (including Mord'rethar: The Death Gate and Aldur'thar: The Desolation Gate) in turn, the efforts of the death knights of the Ebon Blade Thassarian and Koltira Deathweaver working with the Alliance and the Horde was what allowed them to pass these defenses during the war against the Lich King.

The death knights sent the adventurers to weaken the gate's defenses by slaying the Harbingers of Horror and Corp'rethar Guardians, and by taking out the Broken Shard of Horror, the Broken Shard of Despair and the Broken Shard of Suffering, which would have inflicted massive casualties upon the upcoming assault force. Once all the missions were completed, the final Scourge defense line was broken and the path to Icecrown Citadel was cleared for the upcoming assault.