Doom(RL) is very bloody game and connotation with blood thirst is nearly-instant. You'll say, that it shouldn't be taken literally. But why? There's chainsaw which isn't quite serious weapon. There's also a spear which our marine would definitely don't know how to effectively use. I think that making an Angel of Blood challange would be another step in that direction - let's make him lust for blood all the time. He doesn't have to be a mystic vampire or a mutant, it's just for fun of all magic red liquid lovers (that means all of us, actually).