It seems that Horde and Alliance each get their own juicy lore goodness in addition to loots, as players will be able to accompany Sylvanas Windrunner or Jaina Proudmoore as they seek a path into the heart of Icecrown Citadel for their individual reasons. (It's safe to say Sylvanas is probably looking to shoot Arthas a lot.) Once inside the Frozen Halls, players must confront the bosses of the Forge of Souls and the Pit of Saron before finally confronting Arthas himself. Sounds pretty bloody epic to me.
The text indicates that each section will have its own unique means of challenging the players before confronting the bosses. With names like Bronjahm the Godfather of Souls (is that a James Brown reference) and Scourgelord Tyrannus, I think it's safe to assume we're not going to be offered tea and crumpets, unless of course they're evil tea and necromantic crumpets.
So there you have it. Go forth and feast your eyes on screenshots of this 'massive, sprawling 5 player dungeon' if I may paraphrase.
Since we know many of you can't access WoW's official website at work, the complete details from Blizzard are reproduced after the break.