World of Raids found a hidden link in Blizzard's latest newsletter. That link has led them to a special page on the official Wrath of the Lich King site that you can't find on the expansion's main page.

On this special page is an extensive exploration of how the Warcraft team designed the Northrend 5-man instance, Utgarde Keep in the Howling Fjord zone. First they delve into the story elements that ramp up to your introduction to the "impenetrable fortress in the side of a mountain." Upon arriving by boat to Daggercap Bay, you will see the damage wrought by the enormous, native Viking race and their proto-dragon mounts.

Overland quests from there will tell the story of how these Vrykul have used Utgarde Keep as a staging area to wage a battle against what they see as an invading force of Alliance and Horde.

The page goes on to explain other design decisions that will play out in Utgarde: as a "starter" dungeon, it's designed to be finished quickly; it will be more mission based due to the popularity of Old Hillsbrad and Black Morass in Burning Crusade; and you will get glimpses of the end boss before finally encountering him.