Originally Posted by Frosstbyte

Absolutely 100% incorrect. When they first announced death knights, there was a lot of community speculation that a question would be required to "unlock" the class because, at the time, it was believed that you would have to convert one of your old characters into a death knight. When they revealed that DKs would start as new, different characters, people clung to the quest chain unlock for non-specific reasons.

To get a death knight out into the world (of Warcraft) all you have to do is 1) have A character at level 55 or above on the server you wish to create the death knight and 2) finish all the death knight prequests from Ebon Hold. Simple as that.