This is a BUG deck I have been trying out for a little while now and am starting to really enjoy playing. It's built on the back of Mono-Black Devotion as a starting ground, because Mono-Black Devotion is a strong deck and a deck I am comfortable playing.
Main Deck
I use Deadbridge Chant instead of Underworld Connections mainly because I prefer it and it synergizes well with Whip of Erebos.
For removal I have Abrupt Decay Bile Blight Hero's Downfall Thoughtseize and Devour Flesh all of which are included for obvious reasons.
Gaze of Granite is also included to have a nice board wipe late game, though Ratchet Bomb can be used if you would prefer it.
For creatures we have the basic Mono-Black Devotion list with an added Progenitor Mimic which works nicely with any of your creatures.
For the mana base I have found the Blue generated from Temple of Mystery and Temple of Deceit enough to be able to cast my Blue spells consistently. For green sometimes I have trouble getting there after side boarding and have thought about getting a few Birthing Pool just to guarantee I make it there, but I don't own any and don't really want to buy/trade for them. If you have them maybe cut a Swamp for 1 or 2 and maybe even a Temple of Deceit if it feels necessary.
Side Board
We have an extra Abrupt Decay for either dealing with creatures such as Brimaz, King of Oreskos Nightveil Specter Pack Rat or to deal with Detention Sphere or Underworld Connections.
Dark Betrayal for the Mono-Black decks or even Mono-Blue for Nightveil Specter.
Drown in Sorrow is a low power board wipe with a small upside.
Erebos, God of the Dead works well with Devour Flesh and is great against U/W Control.
Gainsay Is an interesting choice. It's great against Mono-Blue, U/W, or even Esper.
Golgari Charm is another answer to Detention Sphere and Underworld Connections. I always bring this in against U/W Control, It can stop a Supreme Verdict, or can be used to kill Elspeth, Sun's Champion tokens to get to clear blockers and kill her if you don't have a Lifebane Zombie
Speaking of Lifebane Zombie I have included him for G/R Monsters, Mono-Green, U/W Control and to deal with Blood Baron of Vizkopa before he hits the board, which is always a bad thing.
I have Mistcutter Hydra just as a creature I guarantee against Mono-Blue and U/W Control.
Thoughtseize is included just for match ups where hand destruction is amazing since I only have three main deck.
And Lastly I have Unravel the Aether to deal with Gods. Thassa, God of the Sea is huge problem if you can't Gainsay it and Erebos, God of the Dead is painful against the black matchup.
Possible Changes
I have thought of cutting Drown in Sorrow for another Devour Flesh and may do it if I face less Aggro/more black.
I want to add 2-3 Duress to the sideboard but don't really know what to cut. I'm leaning toward 1 Erebos, God of the Dead and Mistcutter Hydra
I would really like another counter spell to replace Gainsay but none look like they will fit well with the deck. Syncopate seems alright but isn't a guaranteed counter with small amounts of mana, and Dissolve is hard to cast with the UU in it's mana cost.The last option would be Essence Scatter which would still deal with Thassa, God of the Sea and also Blood Baron of Vizkopa but wouldn't help with Sphinx's Revelation.
