Blood Magic, Demon Knights, and Vampires

[Baalz]

Yes it does, but on immortal kamikaze units that doesn't really matter. Even if you're pretty terribly horror marked (20+) you don't get a horror attack anywhere near every round. As long as you stay in dominion and don't give them items (as befits a kamikaze squad) then it doesn't matter terribly much if your guys are occasionally eaten by horrors. Granted, you don't want to horror mark them for every border skirmish, but it is a small price to pay if you use it to kill a big scary army.

If you're particularly wicked have an otherwise tough dude equipped with two shields of the accursed run forward to let the enemy's front lines whack at him for a couple rounds while the communion is going off. Now those hell power spawned horrors just add to the carnage instead of working against you. Unless he's berzerk your shield wielder will quickly get overwhelmed by fear from the horrors drawn to his location and book it out of there so you've a good chance of him living considering he's got +18 defense from the shields.

[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.

[Valandil]

Demon Knights are wonderful troops, indeed, B5 mages aren't actually too rare: Athame+Brazen vessal on a regular B3 dude works.

In a recent game, I had a god up to B12, casting infernal crusade when I could.

Well, up until about when my demon knights discvered that they weren't shock immune.