

Ghostcrawler stated that there would be 31 bosses in the Citadel, but later admitted it was a joke.
#ICC GUNSHIP BATTLE SOLO PATCH#
The fourth wing was opened with content patch 3.3.2 on February 2, 2010.

The third wing, the Crimson Hall, was opened two weeks later, on January 19. The second wing of the Citadel, the Plagueworks, was opened on US servers on January 5, 2010. Any heroic modes may not be attempted until the Lich King has been defeated on normal mode, and you cannot face the Lich King on heroic mode during that week's lockout unless you defeat Putricide, Lana'thel and Sindragosa on heroic mode. The Lich King may not be fought until Professor Putricide, Blood-Queen Lana'thel and Sindragosa are dead. There was a period of some weeks after the opening of the first section before going on into the second. Icecrown Citadel is split into four sections since release, in the following order: The Lower Spire (the first four bosses), the Plagueworks (the next three), the Crimson Hall (the next two), and Frostwing Halls (the last three). To enable it you will have first have to have defeated the Lich King on normal mode, and heroic mode does not affect trash in any way and only changes the bosses.

Such as, you cannot change the difficulty in combat or during certain scripted events. Some restrictions on when you cannot change it are in place. It is also able to be switched at any time during a raid without leaving and reentering the instance. Icecrown Citadel is home of the updated instance difficulty setting which can be changed on a boss per boss basis.
