Please note that what follows are the personal speculations of the author.

Now many of you maybe asking yourselves " Why drink Blood from Vampires? they get their blood from humans. Wouldn't it be easier for a creature that can beat and feed on a Vampire to get the blood from humans?" Now I have a couple of theories of why this might be. They may or may not be dead on right but it should give you an idea.

The first theory:

The theory is that once the blood enters a vampire and becomes its own the properties change, it becomes infused with supernatural energy. The vampires use the energy to maintain their otherworldly powers like fast regeneration, super speed, flight, etc. So the Black Angels feed on the processed blood to process it even further to achieve higher powers.

Thus ataining it from humans it would not have the same nutritional value. These creatures can also eat normal human food, however they don't like it as much and need (obviously) more than the avarage person. Unlike vampires they can digest things other than liquids (however it is harder for them but not impossible). They would obviously prefer the blood of a Vampire rather than some steak.

The second theory:

It has been suggested that Vampires drink blood for their plasma, because their bodies can't produce it any more and because they can extract their nutritional value much more effectively through liquids (obviously solid food does not agree with them). However its supposed that Crusniks/Black Angels don't need the plasma because their bodies can produce it, thus its just better to get blood with out plasma. Also, based on the idea that a stronger being requires more energy to function than a weaker one, a Vampire is more nutritional than a human is and of course the blood has different properties, it makes more sense for the Crusnick to go after one Vampire rather than a bunch of humans.

The Third and final theory:

It also has been suhgested that Vampires go after humans for their "life" energy in their blood. As you might guess the life energy is not only energy stored within the blood but the will of life; the person's energy, if you will. So, if a Vampire drinks the blood of humans for their life energy because its already dead (a Vampire is a corpse brought back from the dead that feeds on the blood of people, by definition), then a Black Angel would be feeding not only on the nutrients of the Vampire's blood, but also on the life energy that becomes the Vampire's from the humans, and the refined energy from other humans. and since a Crusnik is presumably not dead, it can create its own life energy, thus adding to it the Vampires and human energy.



However they do rather Constant Blood vampires. That is to say Vampires that feed constantly and often on humans. Which is often because the hunt indiscriminantly, which is likely to be classifieded as "evil". So it could they be are classified as some kind of "knight" in our favor.