I think the cards in this deck must fit into 3 requirements;
1. Create advantage (or don't mind much) when itself dies:
Gravecrawler - Cheap to cast and to return from GY. In early game, its fast. In late game, can be sacrificed multiple times each turn.
Geralf's Messenger - Deal a minimum of 4 damage when sacrificed once. "Flashback" it with Lily or Relentless Dead!
Abyssal Persecutor - When sacrificed, in fact, we solve the drawback.
Bitterblossom - Generate bodies (to be sacrificed) each turn.
Relentless Dead - Nice recursion, devotion and helps Gravecrawler and can return Geralf's Messenger.
2. Create advantage when others creatures dies:
Blood Artist
Grave Pact - incredible board control.
3. Sac outlets (usually with a advantage associated):
Viscera Seer - Major enabler.
Bloodthrone Vampire - Cheaper and faster than Nantuko Husk, can eat the crawlers, faeries and Geralfs to attack or to become a nasty blocker.
Phyrexian Obliterator - Devotion for Nykthos. A tricky problem for the opponent.
Altar's Reap - The drawback isn't that bad for the deck - can even help to avoid exile removals.
The removals:
Go for the Throat - One of bests removals in format.
Tragic Slip - Morbid triggers all the time.
Hero's Downfall - Wide range removal, to deal with planeswalkers.
Others functions of the enablers/removals are solve the Abyssal Persecutor drawback and to avoid exiling removals targeting recursive creatures, such Path to Exile on Gravecrawler.
Tools to help minimize Monoblack drawbacks:
Mind Slash - because the best time to remove enchantment/artifact is before they hit the battlefield. Duress is in the SB if you need more speed.
Phyrexian Arena - 'Kind-of-broken' draw engine. A personal black staple.
Due the nice devotion, Nykthos, Shrine to Nyx works quite well.
