How about a death spiral? It's easy with a massive integer loop spawning from 1 to 36, then simply reverse it to make a complete circle, if done correctly with the right SFX, will look awesome. Exists in the database somewhere.
Last thing I can think of, is like a giant shadow dummy dragon with thin transparency and no tint that arises from the death knight's body, and then whatever bonuses you want. It's kind of likt Bladewing's Thrall
Death Spiral already exists into the spells section. Search for Darky's first spells and you will find there some good spells for a Black Dragon. The Spell section is full. Just set the section so it shows you ALL spells (yeah... pretty much) and search for a nice looking and prolly with nice effect one. Unfortunately, for such a quick scout you can only base on Description. Oh well...