Ulduar is a raid dungeon in the Titan complex of Ulduar, located within the The Storm Peaks. It serves as the prison of the old god Yogg-Saron as well as the current residence of most of the titanic watchers who have fallen under his influence. It is notable for its interactive ways of starting hardmodes--instead of switching the difficulty of the encounter before fighting, players would have to start the encounter in a certain way to unlock the hardmode. For example: defeating Thorim's gauntlet in 3 minutes or less would trigger his hardmode.

The Yogg-Saron hardmode is especially notable for having varying degrees of difficulty. In the basic version of the encounter, players receive assistance in the form of buffs from all four Keepers. If players do not speak to a Keeper before pulling Yogg, they will lose that Keeper's buff.

Ulduar also has an extreme amount of achievements associated with it. There are numerous ones that are not required for the meta-drake. In later dungeons, the number of miscellaneous achievements was toned down.