Ripped from Blizzard!

All across the lands of Northrend, many battles have been fought against the vile Scourge. Countless lives have been lost since the Alliance and Horde first reached the frozen wastes, but the champions of Azeroth continue to march forward. Now Icecrown Citadel, the cornerstone of the Scourge's power and the home base of the Lich King, is their final target. Tirion Fordring and the Argent Crusade have forged an alliance with Darion Mograine and the Knights of the Ebon Blade to form the Ashen Verdict. The strongest combatants of this coalition, along with the champions of the Alliance and Horde, will lead the charge against the citadel.

This dungeon reveals the culminating story events and battles of the Wrath of the Lich King expansion pack. Join the legendary heroes Highlord Tirion Fordring, High Overlord Saurfang, Muradin Bronzebeard, Highlord Darion Mograine, and King Varian Wrynn in an epic battle against the Scourge and their master. Icecrown Citadel features 10- and 25-player versions of the raid dungeon, and each version has 12 encounters. Each encounter can be fought in either normal or Heroic mode, and players can use a new user interface feature to toggle easily between difficulties. The rewards in the raid dungeon start at item level 251 in the normal mode with 10-player encounters, increase to item level 264 in the Heroic mode mode with 10 players and the normal mode with 25-player encounters, and then finally reach item level 277 in the Heroic mode with 25 players.

Grand Entrance of the Citadel
After breaching the fortress, players will face a legion of undead guards directed to repel any invaders. Commanding the defenders is Lord Marrowgar, a monstrosity fused together from the bones of the undead. Supreme Overseer of the Cult of the Damned, Lady Deathwhisper is the next opponent. She bolsters the faith of her followers by promising them the opportunity to give eternal service in undeath.

As they continue their ascent, the Alliance and Horde heroes ultimately end up outside of the citadel where their hatred for one another erupts into a battle for dominance over the Rampart of Skulls. Players will join in battle alongside High Overlord Saurfang on the Orgrim's Hammer gunship or Muradin Bronzebeard on The Skybreaker in a unique encounter. Each faction will protect its gunship and try to destroy the other one in a back-and-forth battle to see who is truly worthy of facing the Lich King.

The Lich King's most powerful death knight then stands as the final obstacle for the heroes to enter the upper reaches of the citadel.

The Wings of Icecrown Citadel
After the heroes of the Alliance or Horde defeat the other faction on the gunships and wipe out the creatures near the entrance, players will venture into an area with three separate wings. Here they will face a multitude of terrors that must be vanquished in order to confront the Lich King.

In the Frostwing Halls players will battle alongside the Ashen Verdict and push into the lair of the deadly frost wyrm Sindragosa, who continues to strengthen her brood with the help of Ymirheim's vrykul. Along the way, the heroes will stumble upon Valithria Dreamwalker, a captured green dragon whom the Scourge is using as a test subject for their own ends....

The Plagueworks contains the most twisted experiments ever produced by the Scourge. In this wing players will face two new forms of abomination in Festergut and Rotface, who currently protect their devious creator, Professor Putricide.

The Crimson Hall contains the leaders of the San'layn, undead blood elves who oversee the Scourge's operations throughout Azeroth. The blood-princes Valanar, Keleseth, and Taldaram were raised into undeath by the Lich King to avenge themselves while protecting their blood-queen, Lana'thel.

The Frozen Throne
After clearing all three wings, players will ascend to the Frozen Throne, where the Lich King and his runeblade, Frostmourne, await to deliver them to their deaths....

Random Notes:

This guy has since been removed from the game files.   Suspected to be the Immolated Champion that you see in Yogg's brain so will turn up in the Arthas fight, maybe.