Patch 3.1: Secrets of Ulduar Launched Thirteen Years Ago

wowhead.com:

On this day, April 14, 2009, thirteen years ago, World of Warcraft Wrath of the Lich King: Patch 3.1: Secrets of Ulduar was released.

Since discovering Ulduar in the Storm Peaks, adventurers have journeyed to the titan city to learn more about its mysterious past. Further exploration has revealed that the magnificent complex is above all a prison, intended to permanently confine the Old God of death, Yogg-Saron. This ancient horror has corrupted its guards, and now it is breaking through the last of its restraints. Faced with the peril of Yogg-Saron's imminent freedom, a band of mortals has made preparations for a sweeping assault on the city. Overcoming the legions of iron minions and towering defenses at the city's entrance will take tremendous strength, but even that great victory may not be enough to overcome the madness that dwells below. Ulduar is often remembered as on of the most epic experiences in World of Warcraft. A massive 14 boss instance with memorable and challenging encounters, exquisite and innovative design, and music that evoked both the grandeur of the Titans and the terror of the Old Gods, Ulduar was highly anticipated and did not disappoint. The raid featured both 10 and 25 person modes, and hard modes that could be triggered within the instance, as well as Fragment of Val'anyr that could drop to allow for the reconstruction of the Legendary Val'anyr, Hammer of Ancient Kings.The Siege of Ulduar

The Antechamber of Ulduar

The Keepers of Ulduar

The Descent into Madness

Celestial Planetarium