Angrathar the Wrath Gate (WoW)  

Angrathar: the Wrath Gate is a huge walled gate that bars the entrance to Icecrown Citadel and is located in the northwest part of Dragonblight. The Wrath Gate is crafted to look like the Helm of Domination and is made of Saronite, a black metal created by Yogg-Saron's blood.

Both the Alliance and Horde are besieging the gate, and have set nearby camps at Fordragon Hold and Kor'Kron Vanguard. If they follow the quests line in Dragonblight, the players will arrive during the height of the siege and will be witnesses to great tragedy. The Wrath Gate event signals the end of the first act of the expansion and a change in gear - the players are now directly involved in stopping the Lich King.

The Wrath Gate event culminates with a cut scene in World of Warcraft, which you can see here. Seeing this video will spoil the storyline of the Wrath of the Lich King, so be warned.

Notes

Wrath of the Lich King required!