So, this is my bid for the MonoBlack Control deck for the format! I think it's handling pretty well, and it needs some more work on the sideboard. However, here is what we have.
Creature Control:
We are running 11 Removal spells, with others that can subsitute in for the purposes of removal. Phanika's Cure, Quag Sickness, and Slum Reaper fill those removal slots. In addition, we can use any of the 4 corrupts as emergency removal, along with Lilliana. With the Whip in play, we have another chance to reuse the Slum Reaper as removal. Overall, it's rare that a creature manages to stay on the board for long.
Thoughtseize deserves mention here. While technically a broader card that deals with larger problems, there have been countless times in testing that a turn one thoughtseize has snatched a key creature from a players hand, and set them back a bit. Don't underestimate it's importance.
Win Conditions:
This deck attempts to use Corrupt and the Gray Merchant to drain life your opponent to 0 life. The Whip provides us with more life gain, and a way to loop the Gray Merchant back into play, allowing for more draining. It's not a fast kill, but we typically have time to get to the kill.
Support:
Whip of Eberos is a roleplayer in the deck, allowing Slum Reaper to reap again, and to allow Grey Merchant to deal more damage from the grave. Absolute all star.
Nightveil Specter provides early support in the means of a blocker and Scry Disabler. It is a canidate to be replaced when a stronger 3 cc creature becomes available, but with it's 3 Black Devotion, it's not a horrible choice.
Liliana loves Corrupt as a spell, and helps enable the win. If she also can come in for a surprise kill with any of the creatures by using her second ability.
Grave Betrayal is a late game play that turns more creature based decks into tools for their own destruction. Having their own creatures come back even larger to use against them is a useful tool.
Underworld Connections is the card draw engine of choice for this deck. Since we have a lot of ways to gain life, it's hardly ever a bother to tap a few lands to get more cards. It's contribute of Black Devotion is really useful.
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Why am I not playing Eberos, God of Death?
I am sure some of you are thinking "Why don't you have the god in with all the devotion?". The simple answer is it's not needed. It takes up a card space, it gets exiled easily enough, and honestly, it doesn't add to the way this deck wants to win. It serves as a good wall, and a more expensive way to draw cards, but Underworld Connections does that job better. Overall, I wanted to put it into the deck, but it doesn't have a home here.
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I look forward to some feedback, and suggestions for the sideboard. Thank you for taking some time to look!