(Advice is welcome!!)
Removal is the name of the game. Lots of ways to take out creatures, pick apart your opponents hand, and a lot of sideboarded graveyard hate. Creatures in this deck have all kinds of value.
Mainboard
Creature Removal
Victim of Night targets most creatures, one of the best removal cards out there.
Dismember Good removal tool. Can get rid of most creatures fairly cheap.
Unmake Hits pretty much everything for three mana. Great card.
Gatekeeper of Malakir This dude is valuetown. Removal and a 2/2 for three mana. Can't beat it. I tend to hold on to him so I can get max value.
Hand Hate
Inquisition of Kozilek This hits pretty much all of the control cards that might give me problems.
Thoughtseize Best control card in black.
Wrench Mind Decent card, nice to use once I've picked their hand down.
Graveyard Hate
Bojuka Bog Talk about value. Destroys graveyards
Card Draw
Underworld Connections Speaks for itself.
Win Conditions
Wicked Akuba
Can be so destructive late game with its ability.
Abyssal Persecutor Good card and I have plenty of ways to remove it.
Phyrexian Obliterator This is a lose/lose situation for your opponent. Unless they have direct removal handy, they are in a bad situation.
Vampire Nighthawk Flying, Deathtouch is good, but what really makes him shine for me is the life gain. It can do a lot to save you in close matches.
Sideboard
Sideboard is mostly graveyard hate and some stuff to deal with artifact decks.
Extirpate Good targeted graveyard removal.
Vampiric Link For dealing with Eidolon of the Great Revel.
Geth's Verdict More creature removal, just in case I need it. Also good to get rid of my Abyssal Persecutor.
Duress Some decks need their hand picked apart more.
Haunting Echoes This just isn't far. This can wreck an entire deck.
Mutilate Just another way to deal with creatures. More for aggro.
Pithing Needle For dealing with those pesky cards I can't remove.
Ratchet Bomb Another one for difficult to remove cards, but takes a few turns.