You run into icecrown and engage the first set of mobs the gate behind you locks up and the LK stands above you on a platform blasting away the floor after you beat the pack. You fall into a crypt where you fight King Leoric the skeletal king.
You make you way out of the crypt only to find at the stairs back up is part of the kingdom and guess who is waiting there for you, Anub'Arak!
You make it into another large chamber where Saurfang Jr., and Bolvar, both with their own unique powerful ghoul...ish thing.
Then you make it out to a garden of undeath inside the citadel. Large trees of bones and hedges of corpses. Sindragosa can be seen nomming on a pile of live mortals in a bone bowl.
A faceless one is chained up litterally like a pet in the next corridor, there are 2 other passages but before you get to choose which of the 3 ways you want to go, he mind controls you, walks you towards him, and traps you in a solid black bubble of darkness with him. YAY!
I'm losing my creativeness so we'll throw in a vargul, and valkyrie fight.
a council type fight with geist, vampire guy, gargoyle, banshee, and abom.
Some random eredar
another couple maws of yoggy
and LK himself
and maybe when he dies the essence of Ner'zhul being once a shaman and now a dk reconstructs his old body and fights you again with his own style of fighting and different abilities.
Then Kaelthas swoops in and grabs frostmourne and teleports to the maw of oblivion, *end of xpac* see you in 2 years!