I initially designed this deck with a vampire/tribal theme and really wanted to include my favorite lock ever: Bloodchief Ascension + Zur's Weirding. But I realized that it may work better as a sideboard WC. Initially was running two ZW's but cut down to one to make room for draw. Just remember, if you're weird about blood, you're probably a hemophiliac...or have some dark fetishes.
Blood Synergy:
Bloodghast + Altar's Reap, Viscera Seer, Dark Prophecy, or Bloodchief Ascension if unblocked.
Bloodchief Ascension gets counter ramp with cheap vampires (Pulse Tracker is an awesome T1 with it.) You can even use Sign in Blood if you're desperate or when you have the lock with Zur's Weirding.
Sudden Spoiling - Just plain awesome. I can't believe this card doesn't see more play. Extremely useful in the combat phase (practically victory assurance if you've pinged 'em down.) Functions as board wipe but also protection from spells your opponents might play in any phase. Forget that counterspell, fool!
Sideboard:
Vampire Hexmage has great sideboard versatility against planeswalkers, creatures that enter with counters (like those annoying Standard hydras), weenie/aggro, etc.
Underworld Dreams is super effective against control decks. Let them draw hard, and then you can ping 'em with your vampire clique.
Imp's Mischief is nice against instant and sorcery heavy decks, and especially spells with (x) in their mana cost since you don't pay for (x) even though they have, and their not going to like the new target much, I expect. Still, not sure if it belongs in the sideboard...
Erebos, God of the Dead - Stop gaining life please! Super easy to ramp up your devotion in this deck. Might be worth running two.
Blood Tribute + Sanguine Bond = Game Over (assuming you can tap a vamp (hint: very likely.) OH! And the humble Exquisite Blood is a nice savior against aggro/red deck wins. Also game over with Sanguine Bond (it's like pooping back and forth forever, but more sexual and with blood...yum!)
Maybe:Perplex a decent counterspell against control and higher mana curve decks. Then turns into an insanely awesome search spell (need I say Liliana of the Veil?) Also pairs nicely with Captivating Vampire, Vampire Nighthawk, & Dark Prophecy. Still...not sure if this is the best sideboard choice. Needs some playtesting.
Consuming Vapors may be useful against crazy amounts of creatures, but I feel like Sudden Spoiling deals with creatures more stylishly/cheaply.
Dash Hopes pairs really well with Bloodchief Ascension and the 5 damage for 2 mana is awesome, but still opponent's choice is fun but not always favorable.
Geth's Verdict could be a good switch out for Feast of Blood, but the life gain from Feast gives it the edge. Though Geth can assist in counter accell for Bloodchief. gravepact seems the best sac engine.
Let me know if you think something in the maybeboard would make a good replacement. Maybe suggestions against mill?