[Baalz]

Yeah, the thing about Demon Knights is its almost always better to do blood stones with anybody who can summon them with the exception (as mentioned above) of Ritual of the Five gates and Infernal Crusade. One nice thing, by the time you can cast Infernal Crusade you can also summon Demon Lords (using just blood magic) and there is at least one (maybe two...I don't remember) demon lords who can cast Infernal Crusade. I find it much more likely to amass them (along with several other useful units) by casting ritual of the five gates. Its a fairly cheap spell for what you get, the only hang up being B5 mages probably aren't falling off of trees - but then again it isn't terribly difficult to get 3 blood boosters.

If you do have earth mages, weapons of sharpness, legion of steel, strength of giants, bloodlust - now there's a damn scary force of hell knights.