- There will be at least 4 floors' worth of content in Icecrown Citadel, which I would guess means it'll be reminiscent of how you worked your way up from the sewers of the Black Temple to the roof with Illidan. They plan to make more use of the warp/teleport mechanic currently used in Ulduar that makes it possible for players to see bigger dungeons without spending a lot of time just running from place to place.
- Sindragosa (the same dragon you saw Arthas raising in the Wrath of the Lich King cinematic trailer) and the Lich King are two confirmed bosses. Based on the "Shadow Vault" scene glimpsed in Yogg-Saron's brain room, I'd wager you'll be seeing Saurfang the Younger and Bolvar as well.
- Once you reach the second floor, you board your faction's airship alongside one of your faction's heroes (Varian for the Alliance, Saurfang for the Horde -- which makes me wonder if they'll play any role in the likely Saurfang the Younger/Bolvar encounter). One of the "boss encounters" sounds like it might actually be fighting the opposing faction's airship on your way to the third floor. Rocket packs are involved (!). Note the docking area on the top of the third floor.
- The third floor (see below) has multiple wings, but the fourth floor is nothing but Arthas. The Arthas encounter was briefly described as being very affected by the environment a lá Malygos, i.e. parts of the floor will break off, but they're saying that there's no rescue mechanic like the red drakes. I would expect a heavily movement-dependent fight.
- Multiple 5-man dungeons will also be part of the Citadel, spanning 8 bosses. You have to unlock most of the dungeons by doing a questline, but after you've finished, you can do any of the dungeons anytime you want.
- Jaina and Sylvanas will both be involved with the Icecrown Citadel storyline.
- As stated, Arthas isn't going out like a punk -- although I don't think they actually confirmed that he dies, just that there's a great cinematic lore moment: "Absolutely. It's going to be awesome, there's no way you're going to be disappointed."
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