Finishers
Powerful creatures that will decimate our opponents life total to win us the game.
Abyssal Persecutor: This guy is extremely efficient. His drawback prevents us from winning even when our opponent has less than 1 life. To solve this problem, we include plenty of removal (Victim of Night, deck:gatekeeper of malakir that can be used to dispose of our minion once he is no longer of any use to us. How deliciously in flavor.
Desecration Demon: Also extremely efficient. Weak to token decks that have plenty of creatures to sac. Otherwise, every time our opponent sacs a creature, we are gaining card advantage and a beefier demon. And if they do not sacrifice, then we have a 6/6 flier for the low low price of ! It's a win for us either way.
Gray Merchant of Asphodel: Our cards have many in their costs leading to a powerful life swing whenever this creature is cast. Casting him on his own is a 4 life swing by itself. With just an Abyssal Persecutor and Black Knight on the field when we cast this creature, our opponent will lose 6 life while we gain 6 life in addition to a 2/4 body on the field. Pretty sweet.
Removal
Black has a massive number of removal spells at its disposal.
Targeted Removal
Victim of Night will kill the vast majority of creatures. Other options include Go for the Throat, Ultimate Price, and Hero's Downfall, which can also target planeswalkers. A key consideration is we want this spell to be able to destroy our Abyssal Persecutor when the opponent has run out of life. So card:Doomblade would not be a good fit.
Dismember will also kill most creatures and can be cast for only with a small life payment. Unfortunately it does not kill our Abyssal Persecutor without prior damage, but it is effective enough at what it does to include anyway.
Gatekeeper of Malakir when kicked provides a sacrifice effect, allowing us to remove untargetable, indestructable creatures, even if they have protection (I think). He is more effective the fewer creatures our opponent is playing. He is also a 2/2 body which is just fine. Even better, we can target ourselves with his ability, providing another way to remove Abyssal Persecutor.
Board Wipes
None included currently, but they are tempting. A few should probably be in the sideboard for creature heavy matchups. Cards like Drown in Sorrow, Mutilate, Bile Blight, Killing Wave, and Virulent Plague can be very effective if our opponent floods the board with creatures while keeping our own large threats intact.
Clears Board vs Kills Persecutors
Drown in Sorrow Clears, but does not kill persecutorsKilling Wave May not clear, but kills persecutorsMutilateCan do both, but requires 6 swamps to kill persecutors
Disruption
Cards that stop our opponent from doing what they want.
Duress: Black lacks for removal of enchantments and artifacts once they are in play. Duress can remove them and along with dangerous instants, sorceries, and planeswalkers from our opponents hand before they have the chance to cast them- all for only !
Board Presence
Creatures cheaper than 4 mana that can hold the board until our big beaters can enter the fray.
Black Knight: First strike lets it stave off overly-aggressive creatures with high power but low toughness.
Vampire Nighthawk: Solid card.
Arrogant Bloodlord: Strong for its cost. Downside may prove to be a problem, so I am not too sure about this one.
Card Draw
Sign in Blood: Two more cards for only and two life.
Sideboard
Changes to Original Decklist
Cards Removed
Waiting to become hellbent for the card draw from Asylum Visitor and Blood Scrivener to come online took too long for my taste. I removed both in favor of other sources of card draw (Sign in Blood) and more combat focused creatures (Black Knight, Vampire Nighthawk).
Pack Rat was also too slow for my taste, so it was removed as well. Without any self discard, Call to the Netherworld got the axe as well.
Cards Added
Duress was included to remove non-creature threats.
Arrogant Bloodlord is a cheap, powerful creature, but his drawback may prove too harmful. I am not sure about keeping him.
Desecration Demon is very similar to Abyssal Persecutor: a 6/6 flier for only four mana. Very powerful, very cheap. Unless our opponent is generating many tokens, every creature they sac to our demon is card advantage for us.