How does one work Death Knights into the lore of World of Warcraft: Wrath of the Lich King? After all, these beings are supposed to side with the Scourge and are considered hated enemies of both the Horde and the Alliance.

Blizzard Poster/ Community Manager Bornakk pointed out that this question was answered in the Lore & Quest panel during the last Blizzcon. In case you missed that though, he provided a summary of the storyline behind the Death Knights and why they're serving the enemies of the Lich King:

The idea is that a character goes to become a Death Knight, is trained as a Death Knight, but then realizes they doesn't want to go through with the evil acts they are instructed to perform. So the character finds a new Alliance or Horde home who accept them as a necessary evil (like warlocks) to help them fight their enemies.