Merciless Executioner is pretty good.

It is good, and it was in the list at the start, as a second copy of Fleshbag. But, I decided that I liked the look of Slum Reaper more. Which, isn't the best reason to not run it, and, putting it in over Slum would be a very easy choice if I felt it needed to be just a bit tighter.

If you're interested I also have a Liliana deck. If you'd like you can take a look: Lili's Revelation

Butcher of Malakir for a Dictate of Erebos/Grave Pact on a nice, beefy, flying stick?

I don't feel that butcher is a good choice for the list. It's a third copy of the effect, and it's at 7. It also is much easier to remove than either dictate or grave pact. So, I don't think it's worth fitting in.

Seening how discard was a main theme of the deck in the details have you thought of running Megrim or Liliana's Caress

i recommend Ashes to Ashes to any black edh deck.

Why no Liliana of the Dark Realms? It's exceptional ramp and removal, then when you're ready, just sac it for your commander.

Most of the time, I want Defiant Lili out as soon as possible. So, I didn't put much of a look into the other Lilis. Dark realms seems good. And I'll go test with her a bit and get back to deciding if she works for this list or not.

Dark Realms Liliana has been tested and I've decided I like Ob Nixilis more. They do basically the same thing, a card and removal. But, Ob Nixilis is more consistent and finds me the things I want which aren't another basic after turn four.

Smokestack?

Oath of Liliana offers a symmetrical sacrifice effect (great for multiplayer), and gives you an additional Zombie token when you flip your commander. Obviously a flavor home run as well.

The flip side of your planeswalker makes everyone discard, so including a madness card or two could be useful. From Under the Floorboards fills up your board with an army of biters and gains you a little life.

Liliana's Reaver is another strong creature with powerful discard and Zombie token creation. Solid card overall.

Victimize is another way to toss Filth into the graveyard while it's in play while also bring back two fatties that can take advantage of the unblockability.

Ghoulcaller Gisa is a splendid sacrifice outlet that builds up your board, and can take over games by herself with another high-power creature.

Liliana's Caress is a cheap enchantment that further punishes opponents while they're discarding cards. 2 life loss to all opponents every turn racks up in value.

Lastly, Cryptbreaker is a way to turn extra Zombies into a Phyrexian Arena-type deal. The fact that it's also a one-drop also makes it pretty solid.

I love flip lili. She's an amazingly strong commander. I have my own deck for her if you'd like to peruse:

Saviour of Innistrad

It is, but it's also nastier to me. Which is a harsh ask. I get value off of mists and can handle discarding easier than other players because I'm expecting it. Pit just messes up my plans more than I think it helps.

Nice deck!

I love this! Internal fangirl squeel haha I have been looking for a solid necro zombie edh but mostly see B/U decks. This looks amazing! My only suggestion would be to add Relentless Undead as they keep coming back and can also summon zombies from your graveyard as they do.

@GuardGamer I don't think Relentless Dead is all that great for this deck. there's currently only 6 cards with creature type zombie. The constant need for mana to invest in it makes it hard to justify a slot. Unlike other recursive creatures in this deck, I can't just have it sit around in the grave until I want it to come back.

Strongarm Tactics is a personal favorite for me in decks like this. Coupled with Dread Return and some cheap fodder, you can get some amazingly powerful creatures out early and cheap, while hurting your opponents.

Why no Nether Traitor or Nether Shadow?

I missed sheoldred in the list the first time I looked through it and thought it was weird that you would not have her... it..? In there. Good thing I looked again, this deck looks awesome! +1!

Also, I don't know if you've thought about it already, but No Mercy is a pretty brutal card too.

Zensunni nether traitor and nether shadow both don't make the cut because they really only work when other cards are doing something. Traitor needs something else dying to come back, so it's only really effective with a different recursion creature to generate value. Shadow's slowness also makes it not worth the slot.

This looks like a blast to play! (and not play against lol). Just throwing a couple of ideas out there for you to consider.

I love that you have Dark Depths + Vampire Hexmage , that's always a fun one. Have you thought about adding Triskelion to go with Mikaeus, the Unhallowed?

I assume that Diabolic Intent often just works better in your deck than Demonic Tutor, but Demonic Tutor does seem more powerful than Beseech the Queen, unless I am missing something. Vampiric Tutor is also awesome.

Toxic Deluge is probably the strongest black board wipe and I think you should be playing it. Perhaps over Crux of Fate?

Leyline of the Void doesn't have good synergy with Rise of the Dark Realms. Has that come up in play before?

You're playing a lot of tokens and AEther Snap seems like it would rot in your hand a lot since you don't want to nuke yourself. I see in the description that it does reset Infernal Darkness, but is it worth it?

Shizo, Death's Storehouse is always a great utility land in black. Just a few thoughts.

UpsetYoMama these are al good ideas. I've thought about triskelion, but I don't think that it's useful without the Mikaeus out at the same time, and unlike Dark Depths and hexmage, there aren't other options for making it work.

Beseech is certainly weaker than either of those tutors, but at the moment, I don't have them. They're in the list of to order though. So, hopefully in a few weeks they'll be in the list.

Toxic is actually in the list! And it certainly is great.

Leyline doesn't have as good of synergy with Rise, but it's also turning any discard into exile. And shuts down any of my opponent's grave and death interactions. Which have been worth it so far.

Aether Snap is also counters, and my meta currently has a frequen Atraxa super friends player, so it's currently worth running. Without that player, i'd probably be running damnation in that slot.

Shizo is good. but, I don't think I have enough targets for it. I've got 6 creatures along with Marit Lage and my commander who usually shouldn't be a creature. If it was any creature it'd be worth it. but as it is, i've been happy enough without it. Especially since most of my legends have evasion of some kind.

Nezumi Shortfang is a cool card. Uts one of the very very few cards that can force discard at intsant speed.and then he punishes your opponents for having no cards.

Maybe Megrim and Liliana's Caress as well.