The deck's win condition is, as per the name "Rainbow" used to describe a DK deck using 1 of each rune, Climactic Necrotic Explosion. The thing that differentiates this deck from many Rainbow DK variants is the inclusion of Queen Azshara, which makes for a possibility of having a much stronger win condition with the aforementioned spell through granting an additional copy. It doesn't even need to be exactly CNE, as Azshara can let you copy other important spells to stall until you get a juicy CNE to finish off your opponent, OR let you do other things through her other treasures.

For more spice, you can include Bonelord Frostwhisper to make CNE playable much earlier than it otherwise is. You can then swap a few cards around to include stuff like Boneshredder or Acolyte of Death for more turns of having mana cheat and card draw to sustain through all that.