Tormented Hero -> Awesome life drain

Bloodcrazed Hoplite -> He grows quicker than you'd think. Also, should your opponent use counters, then he's is awesome.

Gifted Aetherborn -> There's just soo much value here. The lifelink in particular is great, but the Deathtouch comes in handy as well

Ashiok's Adept -> Simply put, he can quickly empty your opponent(s) hand. Great stabiliser.

Agent of the Fates -> A decent body in itself, but absolutely brutal against creature-heavy decks. Doesn't care about Hexproof or Indestructible.

Spells

Aphotic Wisps -> Fodder for your heroics, but also draws you a card. Can also be used on opponents creature in a pinch.

Virulent Swipe -> Amazing card for the deck. You get to target your heroics twice. The damage bonus is sweet as well.

Defile -> Great removal-tool for a mono-black deck.

Wrench Mind -> Gets rid of a lot of stuff.

Funeral Charm -> Versatility in a card. One of the few discard spells that can be used at instant speed. Target your opponent on their upkeep if you've already run them out of cards. Can also be used to target heroic on some of your own creatures, especially in a black matchup.

Supernatural Stamina -> Sweet combat trick that helps you keep your board-state.

Auras

Kaya's Ghostform -> Great protection for your creature, especially with all the Path to Exile in the format. Also great with your Deathtouch creatures, so that it doesn't matter as much that you block with them.

Vampiric Link -> Helps you stay alive for a little while longer. Works wonders on your opponents creatures. Also hilarious on a Eidolon of the Great Revel

Lands

Castle Locthwain -> Some much needed card-draw. Buy more of this if you can.

Sideboard

Divest -> Main card against artifact decks. Swap this with Wrench Mind for added efficiency.

Duress -> Just a really great card, so this finishes the playset.

Nihil Spellbomb -> The go-to graveyard-hate card for black if you're not interacting with it yourself.

Damping Sphere -> High impact card against Tron, Titan or Storm decks.

Defile -> Super targeted removal, that increases in efficiancy.

Languish -> Decent board-wipe should things get out of hand.

Dash Hopes -> Good card against control type decks, they rarely expect this. Also hilarious to use when your opponent tries to Temur Battle Rage their Death's Shadow.