If you think you can afford it without ruining your interaction set-up, I would recommend some removal spells just in case you're playing against a deck that runs creatures too. Dismember and Go for the Throat are the ones I'd recommend most highly.

Thanks, @centerlotguardian. Have Victim of Night which does pretty well in here. I was considering Slaughter Pact or Dismember in the sideboard if I need more removal. I'll go with Dismember.Thank you!

A fun black card is dash hopes. A black counter spell unless the opponent pays 5 life

Excellent! I'll give it some play testing. Thanks GreenHorn

No problem. I run it in my u/b faeries and will tap out blue to trick them and laugh

Don't run 4x of Urborg, Tomb of Yawgmoth. It's legendary, so if you get a second copy then it's worthless. I would run it only as a 2x of.

Thank you, lemmingllama. I had only been running 2 or 3 in early testing. It didn't work. The lack of flexibility in any of the mana costs (almost no colorless) along with running more than 4 colorless lands was really not working. It has helped more often than it has hurt, especially against Merfolk and Spreading Seas type shenanigans. When I bumped it back to 4 I had far less issues.

Crypt Ghast, Magus of the Coffers: for more mana ramp?

Lashwrithe: One of my favorites to run in mono black.

Dash Hopes ,and or Temporal Extortion: The baits.

Tragic Slip for Dismember? Or run 2 of each?

Nirkana Revenant = Crypt Ghast + Nantuko Shade

Whip of Erebos: Because too good.

Hypnotic Specter: Can get quite annoying.

Memory Plunder: Was just looking at this card and thought to bring it up

Hopefully I didn't put any illegal cards in here, I usually play vintage with a bunch of friends.

Anyway... +1 Interesting deck. Good Luck with the rest!

love it, +1 from me!!

Firstly, before I get into possible additions/changes. +1, love the concept.

Now, onto some ideas.

Drops:

-1 Urborg, Tomb of Yawgmoth I know this helps, and is good with the deck, I would personally only run 2, but I can see 3 with this level of importance to you. However, I think 4 may be too much. However, as you said you have play tested with only 3, you would know the occurrence rate better.

-1 Nykthos, Shrine to Nyx Great Choice for the deck. You cannot afford to get 2 at a time. So as with Urborg, I would go to 2, but can see your need for it to be at 3.

-1 Desecration Demon He is a fun card, and I like the idea of using him, however, you have better options for the same mana.

-1 Nantuko Shade or Oona's Prowler Love em both, but Shade is ok early game (pretty easy kill, unless you lock out some mana that you can't use in response), and the prowler leaves open discard options for people who work off of the graveyard (since you have no hate for it).

-1 Bile Blight Good Sideboard idea (damn those Merfolk), but it would replace Dismember or Tragic Slip.

-1 Black Sun's Zenith Great Card, once again, to me it would replace one of your removals. So only keep 3 here.

-1 Chalice of the Void If it isn't a mainboard card, then you don't keep 4 around. You will always need the 1 space for your main deck design. (that is how it always works for me somehow)

Move to Sideboard:

3 Guul Draz Assassin Move him to Sideboard. Bring him in if you need prolonged removal. But otherwise, I would use something with greater range.

OR

3 Emissary of Despair Only use him in sideboard over the Assassin if you continue to have too much trouble with affinity.

Additions:

+1 Lashwrithe This guy to replace the Shade or Prowler. Great card. Is another creature to count, plus works great offensively with your Wisp.

+2 Tragic Slip Replaces the Lands. Now maybe you need the 24, maybe not, but -1/-1 gets rid of some annoying creatures early. and can demolish bigger guys later on.

+3 Profane Command Replaces the Assassin. It covers a large group of ideas, but increases your overall average cost. Your deck already seems to take you to mid/late game rather than early/mid. But this card is solid in both mid & late.

(This leaves 1 spot open, but it is something that I would make a couple ideas for. Then let you decide.)

(1) +1 Whip of Erebos Works with your Merchant to recover him and double his effect. Plus you could recoup a Shade or other guy and suddenly kick some ass.OR(2) -2 Gray Merchant of Asphodel & +3 Korlash, Heir to Blackblade ... With Profane Command available, I would totally replace your Merchant. This guy is better for you than Des. Demon as well, since his Grandeur gives you a double land fetch.

Once again, these changes are just ideas. As you know your deck better than me, you could probably see any potential issues I cannot foresee without play testing.On a side note, having read this list, I may throw this together to play test at my local shop. I would rename the deck tho...

FRENCH PHYREXIAN NINJA FRY (gotta honor the creator)

Thank you for all of the suggestions, Yarg and Hazezeroking!

Okay. Dropping Desecration Demon for another Lashwrithe. Wanting to run 3-of Lashwrithe but testing Herald of Torment in the third slot for now. I think that running 1 or 2 of might not be a bad thing due to the bestow mechanic.

I tried Profane Command as a 2-of in early testing. The problem is that running more than that hurts me statistically because I don't want to have that card in my opening hand - at least I didn't with the deck what it was then. Its a top-deck battle winner, but this deck fails if I can't get things onto the board to get Nykthos working. I'll consider it again since the build has matured somewhat since then.

Whip of Erebos - I'll try this one sometime this week and see about Gary/Whip combos. Which leads into the next discussion:

Korlash, Heir to Blackblade - This is a card that has bounced in and out of my TCG cart since I started this build. I considered him, and continue to consider him, but the reason I've shied away from him so far is the same reason I shied away from Lashwrithe at first. The deck isn't about accumulating swamps, as much as it is about accumulating devotion. Sometimes they run hand in hand, but sometimes I am dropping a Phyrexian Obliterator or Grey Merchant of Asphodel on the board on turn 4 with 2 swamps and a Nykthos, Shrine to Nyx. The Obliterator's role was originally to just be a functional devotion tool (its the only permanent that costs BBBB in modern, its just a bonus that it kicks ***). But the build seems to have shifted away from Gary-centric. Korlash is tempting, though. I'll have to re-evaluate the overall strategy and see how Nykthos-dependent I want to be. Having the versatility of Korlash helps prevent Ghost Quarter shenanigans, and also if I don't draw a Nykthos its another strategy. This might require more than just an addition/subtraction though. I'll keep you posted, and definitely test it out digitally for a while.

Enough rambling.

I did just notice a nice synergy between Profane Command and Emissary of Despair (fear). The reason I'm so affinity and merfolk focused is that is what dominates my meta here. There are 3 affinity, and 2 merfolk decks that own the top 4 most Saturdays. Its time for their throne to fall. Profane Command deserves another look at this point.

@Hazezeroking I dig the new name, though! Let me know how your test goes and what changes you make.

Oh, and here's a fun trick that prevents Nykthos, Shrine to Nyx from being a dead draw:

Its turn 4, I have some heavy hitters in hand and a a Vampire Nighthawk, Will-o'-the-Wisp, Nykthos and 2 Swamps on the board. I want to play Phyrexian Obliterator and I'm praying to draw a swamp or Urborg, Tomb of Yawgmoth. What happens? I draw Nykthos - CRAP! ... But wait?

Tap out the first Nykthos, I have 3 mana available from the devotion on the board. Drop the second one from my hand. Legendary rule kills the first and the second comes into play untapped. Use 2/3 mana to tap out the second one. I now have my necessary mana to play the Phyrexian Obliterator. After this turn with Nykthos out, I still have enough mana to do whatever I want do to the devotion. Its not quite a dead draw that it appears to be at first.

This may seem like a corner case, or just a cute trick. But it is such a common scenario its ridiculous. The same trick often works to drop an Obliterator and Gary in the same turn often. This is what lead me to originally consider Profane Command, with 5 or 6 devotion on the board... its insane.

Hey, did you think about Stromgald Crusader? it has protection from white (bye bye path to exile) and can abuse of extra mana from devotion.

Other options, Bloodghast, Gatekeeper of Malakir

And this is just me because I loved the old cylce of deities from shadowmoor and morningtide and you said that you'd consider droping the Gray Merchant of Asphodel. With a good black devotion ramp you could fit one this guys Demigod of Revenge,Ghastlord of Fugue or Deity of Scars. Of course Korlash, Heir to Blackblade is just awesome and kicks ass.

oh and +1!

Definetley Gatekeeper of Malakir and Liliana of the Veil. Also try out some Pack Rats and Inquisition of Kozilek, Duress or Raven's Crime (whichever you prefer).

Ando if you want to go more aggro, then try Bloodghast and Demigod of Revenge which is the best of the a shadowmoor black things. Doesn't hurt that they add tons of devotion.

*Also

Another thing is that you should run 24 lands and that Batterskull is better than Lashwrithe, even in mono black.

Bloodghast

Have you found success with Guul Draz Assassin? I love the art on that card

yo you NEED to run at least 2 or 3 Gatekeeper of Malakir , its an amazing card for removal and it offers 2 black devotion. Also you should run Thoughtseize and/or Inquisition of Kozilek for hand-hate/ removal. As for 4 Urborg, Tomb of Yawgmoth , i personally think thats a terrible idea.. its a legndary land, as has been said, if you see more then 1 its a dead card. Besides that the decks loooks cool +1 for sure but definately could use some tweaks.

Lots of great thoughts here! Thanks everyone!

@betuman - Thanks for the redirect to the demigods. I looked at Demigod of Revenge and considered it heavily in the early stages here. A lot of devotion gets added, but I need to rethink the curve to incorporate. Definitely correct on Bloodghast. That was an early drop that should have come back in. I've considered Korlash, Heir to Blackblade more than once. I'll probably have to go back over that decision.

@pumpkinwavy - Good suggestions. I have a tough time with Gatekeeper of Malakir right now. Mostly because I consider him pretty vanilla 3 drop. I'll maybe give him another test, and keep him as the first to sideboard if needed. I was running an odd number of lands earlier because of Arena. Its a great effect with the Phyrexian Obliterator, but it produces no mana.

As far as Liliana of the Veil, Thoughtseize, Inquisition of Kozilek and Raven's Crime - These are all great cards, no doubt. And I particularly love them in 8-rack. :) But I ran Inquisition of Kozilek and Thoughtseize for a while and was underwhelmed - surprisingly. Maybe its because I'm used to their compounded effectiveness from other archetypes or amplifying effects like Surgical Extraction. But they didn't seem as good of a fit here, at least not yet.

Now: Liliana of the Veil? She may be great, or she may flop in this deck. I tend to have, and want to keep, everything that I have in my hand between turns 3 and 5. So her +1 will go unused for a short time. Since she can't defend herself with tokens and she's competing with some other strong 3 drops I think I'll leave her in 8-rack.

@Nef - Guul Draz Assassin requires a LOT of thought to be effective. Its a solid 1-drop, though, and he's a little scalable which helps drawing him mid-game (not Student of Warfare status, but nothing is). It just requires that you know the archetype you're playing against in order to use him effectively. If I have to sideboard, though, he is one of the first to go. He definitely pulls his weight against decks that rely on their 1 and 2 drops.

As to Urborg, Tomb of Yawgmoth - I'll update the comments.

Smother is good for dealing with Inkmoth Nexus more discard Inquisition of Kozilek|Thoughtseize can help too.

How about some Tasigur, the Golden Fang?

I'd think Tombstalker would be more beneficial than Tasigur, the Golden Fang but hey mana costs.

Even though his fellow rats don't count towards devotion (correct me if I'm wrong) Pack Rat could give you an alternate win condition

Also more removal maybe hand disruption?

Actually, the Pack Rat copies DO count towards devotion. Since it makes and exact copy of the card, the mana cost is included.

Looked up a few websites and I do stand corrected! Thanks pumpkinwavy!

The more you know

Yeah I learned that during the era of mono black in standard. Anyway, Gurmag Angler could be considered over tasigur orTombstalker.

Thanks everyone for the continued feedback!

Tasigur, the Golden Fang is interesting, but this deck doesn't generate a lot of graveyard early enough for him I think. Same with Tombstalker, but I've been toying with those ideas in my 8-rack build and I'm likely going that route or Gurmag Angler in there. But that's not what we're here to discuss.

As far as hand hate (Thoughtseize, Inquisition of Kozilek, etc.) I've not really considered them because I assumed it wouldn't be good because of the lack of devotion help. But those cards can certainly win games. What would you take out APPLE01DOJ? I've taken out Herald of Torment and Gatekeeper of Malakir for 4x Thoughtseize at this point. Let me know what you think.

Pack Rat - Interesting! I'll explore this one further. The amount of devotion gained might be too slow, but I'll test it.