For millennia, Ulduar has remained undisturbed by mortals, far away from their concerns and their struggles. Yet since its recent discovery, many have wondered what the structure's original purpose may have been. Some thought it a cit, built to herald the glory of its makers; some thought it a vault containing innumerable treasures, perhaps even relics of the mighty Titans themselves. Such speculations were wrong. Beyond Ulduar's gates lies no city, no treasure vault, no final answer to the Titan's mysteries. All that awaits those who dare set foot in Ulduar is a horror even the Titans could not, would not destroy, an evil they merely... contained.

As the next step in tiered raid progression in Wrath of the Lich King, Ulduar is set to let players enjoy gorgeous setpieces, sprawling battlefields, and innovative boss encounters. Ulduar's design aims to provide a fun, unique, and innovative raid experience, and it includes additional challenges and rewards for seasoned raiders. In this sneak-peek at World of Warcraft's newest raid dungeon, we'll take a look at some of the new content that makes Ulduar stand out.

Many players have already gotten their Wrath of the Lich King raiding feet wet in Naxxramas and the Sartharion raid, but Ulduar is the first example of the expansion's much larger, truly epic scope of raiding, as will be evident from the moment you set foot in the instance. The most obvious difference between Ulduar and its predecessors is that the new dungeon actually comprises two separate raid areas. The first section is an epic battle against a vast army standing between you and the entrance of the dungeon proper; in the second area, you will dive into the heart of the dungeon itself and finally discover the secrets of Ulduar.

You and your friends will have to use these vehicles wisely to break through Ulduar's defenses. A mix of Choppers, Demolishers, and Siege Engines will be at your disposal, each granting unique abilities to the pilot and the passenger. Chopper drivers, for example, can create pools of liquid tar that snare opponents and can be set on fire by area effect attacks, while demolisher passengers can load themselves into the vehicle's catapult so that the pilot can launch them into the distance. If used judiciously, these and other abilities will help decimate the iron army and any other threats lying in wait between you and Ulduar.

One such threat is the Flame Leviathan. Once you've plowed through the innumerable ranks of the iron army, you will be confronted by an enormous tank. Mimiron built the Flame Leviathan as part of the V0-L7R-0N weapons platform, and as a result, this tank packs quite a punch. Normal spells and abilities won't be enough to take down this juggernaut, so you'll have to rely on your siege vehicles to outmaneuver and defeat the boss. After wearing down the massive war machine, you will have to launch players onto the tank's back to destroy its defense turrets and sabotage the Leviathan before you can move on. If you'd like an additional challenge beyond this frantic (but fun) fight, you can try your hand at one of the Flame Leviathan's different Hard Modes (see sidebar).

Of course, the vehicle gauntlet, the Iron Army, and the battle against the Flame Leviathan are only the start of World of Warcraft's most ambitious raid to date. Patch 3.1 will hit the Public Test Realms very soon, so you will be able to see for yourself what other challenges await beyond the gates of ancient Ulduar.

Ulduar clearly illustrates the new design challenges and innovations that come with the bigger scope of this expansion's raids. In order to make raid content more accessible, a raid has to offer a lot of variety, but it also needs to include a very granular means for players to adjust the raid's difficulty. This concept was first realized in The Burning Crusade with the introduction of Heroic mode, and Wrath of the Lich King is developing the idea even further with new Hard Modes.

Boss fights that have a Hard Mode are affected by certain variables that players can control and that change the encounter's difficulty. For example, spread throughout Ulduar's vehicle section are four Defense Towers you can destroy. The more Towers you leave intact, the harder the encounter with the Flame Leviathan will be, but the loot will also be better.

Ulduar isn't the first dungeon to include Hard Mode, but it certainly makes the most use of it. Out of 14 bosses, 11 will have a Hard Mode that offers additional challenges and rewards. Ulduar will appeal to a wide range of play styles, and the dungeon also has great longevity and high replay value.

Ulduar's new master has rallied a massive iron army to guard the entrance to Ulduar and prevent any unwanted guests -- including you, especially you -- from reaching the inner sanctum. Thankfully, you'll be able to face the Iron Army on even footing: a small fleet of siege vehicles will be on hand to aid you in the assault.