A Whip of Erebos would do the trick. Missing 3 damage to finish off your opponent? Bring back your Merchant to steal away his life for you! Your opponent has a new shiny green/white card? Lifebane Zombie it is!

BestPandamanEU You ARE aware that Lifebane isn't legal?

Welllllll that's why this deck has it and is standard -_- and actually I thought Whip has only 1 devotion so you can kill your opponent off from 4 hp*

Actually this deck went out of standard last friday. valendras is correct about the zombie. Maybe you werent aware of the rotation? The Ravnica block rotated when Khans came out.

I actually have another Mono-Black devotion deck on my profile for post rotation standard if you wanna check that out. mono black devotion khans

Welp. Apparently my deck shares its name with another deck. Well if you wanna see it go to my profile lol

If you can afford it, Phyrexian Obliterator goes well in any black devotion deck

No Pack Rat? :D

Liliana, the Last Hope is also very good. A copy of Erebos, God of the Dead against Kitchen Finks combo, Wurmcoil Engine, Batterskull and any control/midrange deck in general could be worth thinking about. Kalitas, Traitor of Ghet and Desecration Demon have both performed much better for me than Phyrexian Obliterator, and surely Fatal Push, Murderous Cut, and Collective Brutality are better than Disfigure, Dismember, and the other more conditional removal?

For reference, here's my list - http://tappedout.net/mtg-decks/damned-devotion/. Would love to hear your thoughts on it!

RingweMakil, Thanks for the comment! It's been a while since I've updated the deck, or even played modern, so forgive me for not keeping the deck up to date. I initially left out Pack Rat because I'd rather have more value for each individual creature, rather than a creature that required some setup. I like all of those suggestions, and I will definitely have to implement some when I revise the deck. I do question the Desecration Demon though. It was good in standard, but I dont know if it's better than the obliterator. Is it just better with dealing with threats?

Oh, so what format are you pursuing at the moment, then?

Well, even in standard there were definitely matches where you'd side out some number of Desecration Demon; it's a liability against aggressive token lists, and certainly is not the most reliable blocker. In Modern, this means Elves, Voice of Resurgence and Kitchen Finks decks, and possibly also Young Pyromancer decks.

Funnily enough, Demon is actually good against Lingering Souls. The fact that he sits there eating a soul a turn means you don't have to end up wasting kill spells on spirit tokens, and there as well flying is very relevant.

But in general, the fact that card is a 6/6 flier for 4 is very very good. It's a quicker clock than Obliterator (although admittedly Phyrexian Obliterator is better against Valakut, the Molten Pinnacle and Lightning Bolt), it's a 6/6 as opposed to a 5/5 (Reality Smasher, Drowner of Hope, Tarmogoyf), and it flies. Flying is hyper relevant a LOT of the time, whether because you need to hold back opposing fliers or end the game unopposed. It is also easier to cast with a manabase of Mutavault and Ghost Quarter.

Thoughtseize into Pack Rat is still good, for obvious reasons; except maybe against Supreme Verdict/Sphinx's Revelation decks. But being able to turn lands and lategame discard into Rats is very very good; and Pack Rat establishes a board presence mid-lategame as well like no other card can. It lets you go up to arbitrarily high devotion counts, and I haven't yet seen the Modern deck that can match an army of rats with their own army. That said, my build is much more discard heavy than yours, so the capacity for me to turn that into lategame power is more important than it is for your list.

Looking forward to the updates!

So you're running Mono Black Devotion without Ayara and Nightmare Sheppard?

Look, she is 3B and you can drop your bomb of a Gary for atleast 7 devotion and then sacrifice with Ayara and immediately drop him again with the Sheppard for 14 damage.

Get rid of the dual colored lands since you're running mono black. if you want other types of lands get cabal coffers or Nykthos. You aren't running a tribal deck so there is no reason mutavault should be in there.

If you start running Nightmare Sheppard switch out those kill spells for stuff like Bonesplinters, deadly dispute so they benefit you even more.

Yarok's fenlurker is also a good addition to add for the exiling of cards

I like what you got here. Reminds me of my old version from 2018.

If you were interested, you can take a look at my version to get new ideas. I run orzhov for side-board options.