Merihem is considered the prince of the spirits or demons of pestilence, and responsible for all plagues and diseases.
How's that for suitable? Diseases being a primary weapon of the Death Knight class and all.
WARNING! SPOILERS BELOW!
Here is a link to a lot of screenshots from the Death Knight quest chain that makes me want to create one immediately! The Light of Dawn.
Having looked at that, I think that the first thing I'm going to do in Wrath is to create a Death Knight and at least play through the starting zone and complete that quest chain before doing anything else. It seems to contain so much lore and awesome scenes that I wouldn't want to go to Northrend on any character before having seen that introduction. I wouldn't want to see Tirion in Northrend before having seen him in the Plaguelands as it would feel like skipping content or seeing things in the wrong order.
After that start I would at least have a basic understanding of what the class can do, making it easier for me to group up with other Death Knights as well as understanding where they are coming from in a lore perspective.