Alrighty. Soooo, you need more removal. Hex is good but to costly in a mono black discard. Try Doom Blade instead. Also, if this is discard, take out Nirkana Revenant for The Rack or Shrieking Affliction . Also, take out 2 Corrupt for Thoughtsieze if you can get them or Duress .

Nirkana Revenant is one of the keys to this deck. Forgot to take out the discard, so it isn't based on discard.

So what is this deck supposed to be then?

Making Nirkana Revenant a huge attacker, or playing cheap Marshmist Titan s or even running their life down with extort or Gray Merchant of Asphodel , while minimizing hand capabilities.

Soooo, mono black control?

Yup.

Ok then. Well, take out your Nirkana Revenant or at least the Crypt Ghast s. You don't need that much ramp. Run Phyrexian Obliterator instead. Also, take out a few Lilliana of the Dark Realms for Liliana of the Veil .

Negate Nullify Spell Blast Essence Scatter found your weakness but I do say if you through in a staff you should be very good. gain tons of life

Throw in a Dark Ritual maybe a Murder

Korlash, Heir to Blackblade

Dark Ritual is banned in modern, Legendaryone. Sorry.

Alright, I love the idea here but I think I can make some recommendations! Let's go:

1. Firstly, as for hand disruption, in Modern right now there are a lot of decks like Storm that barely use creatures at all, and Zoo that has nothing in it over 3 CMC. For that reason, Thoughtseize and Inquisition of Kozilek are the preferred methods for hand disruption.
2. Next up, there seems to be a ton of ramp in this deck without much to do with it. If you wanted you could try adding something like Griselbrand to ramp to with your Nirkana Revenant , or Exsanguinate . Alternatively you could try drawing more cards. Blood Scrivener is often pretty weak, so you might want to try Sign in Blood or Phyrexian Arena for some more aggressive draw power.
Next up, removal. I see you like your Doom Blade , but how about trying something more versatile like Dismember ? Since Modern games are aggressively costed you rarely get creatures with more than five toughness to deal with.
3. Go 4x Korlash, Heir to Blackblade . The point of the Grandeur ability was so that you could gain advantage from having four of your legendary creatures out, so why not use it?
4. For the sideboard, cards like Grafdigger's Cage , Pithing Needle , Damnation , Suppression Field , Nihil Spellbomb and the like are all strong. You should put some time into finding cards that are specifically powerful against decks you have trouble with. Maybe Mutilate could destroy aggressive decks like Robots and Zoo? Try it out!

I feel like since you have the color for it, Victim of Night over Doom Blade is better. If they bring a black deck to the table also you're screwed with the blade, but victim will still have game. Also Gatekeeper of Malakir and Geralf's Messenger could be good in this build with Grey Merchant of Asphodel. The kicker on gatekeeper is super easy to hit in mono black, obviously.

Also, definitely go for Inquisition of Kozilek over Appetite for Brains . Cripple them early, take out the kneecaps so they can't get to the late game as easily.

I would most definitely take out 2 Swamp for 2 Nykthos, Shrine to Nyx . I feel like your devotion would be crazy high most of the time.

Go for the Throat is an upgrade to Doom Blade in modern i would recommend swapping Doom Blade

mrkoyoyo, I'm not so sure about that. Running Go for the Throat makes game 1 against Affinity almost impossible to win. I would go with Dismember .

Victim of Night would be the best option aside from Dreadbore , Terminate , Abrupt Decay , Maelstrom Pulse , or Path to Exile which of course are in different colors. Dismember is a good option too though because if you have the life it's easy to do multiples of them with the Phyrexian mana, and you have lifegain maindeck.

Yeah, Victim of Night is a good choice, too.

To make the point, Gatekeeper of Malakir doesn't have Multi-Kicker, the opponent will only sacrifice one creatures as you can only kick the spell once.

I think maybe adding Expedition Map and a single Arena could be very strong. Expedition Map can tutor up a Nykthos, Shrine to Nyx , and Arena + Phyrexian Obliterator is an amazing combo.

I run a set of Leechridden Swamp in my Korlash deck, since they can be tutored for using Korlash's ability. Korlash forces them to CIPT anyway, so the tapped clause isn't that big of a deal. You can check out my Modern black deck here! - Korlash's Deathtouch!

I'm surprised there's no Nightmare or Quag Sickness . Speaking of, Quag Sickness gets rid of those pesky Theros Gods (or anything else that's indestructable), so you might want to try it out.

I had Quag Sickness originally, Nightmare is going in for sure, thank you.

Hey dude. I've got a few suggestions for you - keep in mind that I'm imagining this in a slightly more competitive light, so feel free to set me straight about any of that.

In my opinion, Staff of the Death Magus and the other staves are unplayable in modern. They're slow and expensive. It costs 3 mana to drop it, and it literally does nothing when it enters. It relies on you doing well, or the opponent having black. Even still, modern is usually a 4 turn format. Assuming the perfect conditions were met (you're both running black, etc) it's still not a great card. I know you've only got 1 of it in the Sideboard, but it's something to keep in mind. :)

If you're playing modern, you need some grave hate. Relic of Progenitus , Grafdigger's Cage (you need one more), or possibly Surgical Extraction . Snapcaster Mage and Tarmogoyf will ruin your day fast without it.

Surgical Extraction is almost a must in this deck. It'll shut your opponent out of anything you put in their graveyard - You can pull key combo pieces, lightning bolts, etc. It's just overall an amazing card. I'd say run some in the main and the sideboard.

Now, if you're going for a less competitive route, you could consider splashing for an infinite combo off Sanguine Bond and Exquisite Blood . Couple that with a Vampire Nighthawk , and you've got some beasty control going on.

Liliana Vess is okay, but I feel she's a bit slow for modern. I'd recommend going up to 2x of the veil. Maybe cut out the remaining walkers for something?

Oh, and Spellskite if you find yourself relying on your creatures a lot.

Hope I gave you some ideas! :)