Let me list the deck first and comment on it later.
Bloodgift demon x2
Desecration Demon x3
Disciple of Bolas x2
Geralf's Messenger x2
Vampire Nighthawk x2
Elite Inquisitor x3
Mikaeus the Lunarch x2
Sorin, lord of Innistrad x1
Liliana of the Veil x1
Curse of Exaustion x2
Oblivion Ring x3
Underworld Connections x2
Faith's Shield x2
Tribute to Hunger x2
Victim of Night x3
Essence Harvest x3
Killing Wave x2
Sign in Blood x3
Vault of The Archangel x2
As you can see, this deck is incomplete. VERY incomplete. it is pretty much just a draft, but here goes my strategy:
It all revolves around getting one of my demons out, using their effects for my personal benefit and either sweeping for attacks or wearing my enemy down with life drain spells. Bloodgift Demon gives me card advantage and a good 5 beater for minor life loss (which is more than nulled by my life drain power, a similar thought reasoning follows the usage of Sign in Blood as a draw engine) and will make it easier for me to draw into my other demons, preferably Desecration.
Desecration is my star. It is a VERY cheap MONSTER. My opponents will want to sacrifice their own cards to stop him, but doing so will only buff my monster up while wearing down their field. Victim will target the creatures my enemy won't want to sacrifice while Tribute to hunger targets the few creatures my enemy will have after all of this (maybe even one that can't be targeted by Victim) and fuel my life back up, which is always a plus. Also, it gets buffed up to hell and back with Mikaeus and provides some pretty cool combos with my entire deck, which just evolves around him.
Griselbrand is just... A beast. It's insanely powerful, it contributes to my life gain mechanic and... do I need to mention his draw engine, and how well it compliments my deck? I don't do I?
My planeswalkers are there to fuel my control aspect and, in Sorin's case, to buff up Essence Harvest, provide a life gaining weenie (good if my opponet does something unorthodox, like barter in blood, to get me rid of my creatures)
Oblivion Ring is another Control aspect I believe benefits this deck and helps me justify bringing in White for Sorin and Vault of the Archangel. While I was on this "White Control" mentality, I came across Curse of Exhaustion and... I loved it. Seriously, if I get this up, my opponent will be unable to do anything to stop me. And will be forced to side in Enchantment hate on a rematch, which could end up making him board out some other threats.
Faith's Shield is a cool tool that I want to experiment with. It provides defense should my Demons get targeted by Victim of Night or Ultimate Price, and could help me swing a Bloodgift demon or Griselbrand through some bad blockers for game. It may not be worth it, but its an option I want to try out.
Last, but not least, Vault of the Archangel...
Lifegain to give me survivability and Deathtouch, to either make my opponent decide not to block or end up destroying all his threats?
Yes. ****ing. Please.