There will be a new hero class called the Death Knight. At 58 I beleive, you can undertake a series of quests to turn your character into a Death Knight at level 60 or, I think, 70 Death Knight with good gear. They have 2 talent trees known as Blood and Frost, I forgot the other, I think. They can summon minions from the fallen bodies of their enemies or summon a horde of them for a short period of time. I forgot all the details though.