EotN's story expands on a storyline alluded to in Prophecies: The Great Dwarf, the patron god of all dwarves in the Guild Wars universe, opposes the Great Destroyer, an entity so fearsome, his name is forbidden to be spoken among the Dwarves. In Eye of the North, you meet and confront the Great Destroyer.
Earthquakes have ripped through the lands of Tyria, Cantha, and Elona, revealing entrances to an underground complex of tunnels. If you think of EotN as a story in three acts, in Act 1, you'll explore the multilevel dungeons (there will be 18, to be exact) and learn about the Dwarves' conflict with the fiery Destroyer.
You'll also encounter the Asura, a race driven from its ancestral underground home by the blazing menace. You'll eventually pass through the Asura's magical gates and emerge from the subterranean passage into a large settlement that’s housing another race, the Norn. (We're told you'll also encounter some "surprises and a few familiar faces.") There, you'll learn that the Dwarves are preparing for their final battle against their ancestral foe, the Great Destroyer.
In Act 2, three story arcs play out; you'll be able to pursue them in any order. In one, you explore the Norn settlement and learn that they are a brawling, feuding people grappling with some immediate dangers to their culture. In another, your search through a lost Ascalon region will take you deep into the Charr homeland, where that race is recovering from the loss of its gods. And in the third, you'll learn that the Asura are preparing to repel the Destroyer incursion with their own brand of supermagic (though they need you to do the heavy lifting).
As each story arc resolves, the threat of the Great Destroyer mounts. In Act 3 of the EotN story, you must fight your way behind the enemy lines to confront the Great Destroyer. This battle will reveal the first clues about the dangers you’ll face in Guild Wars 2.