So ive started building mono black cant decide if i ahould got b/r. (For thr temples) it opens rakdos return dreadbore etc
Or 2nd option since.nightveils arent in my deck seems less appealing
The b/u

Land base currently is
21 swamp
4 mutavaults
1 nykthos
Rest is...
4 pack rat,3 lifebane,4demons,4 gray merchant, 2 herald of torment, 1 liliana of the dark realms
4 hero's downfall,4 thoughtseize, 2 devour, 2 ultimate price, whip, 3 underworld conn.
SB
1 elixir of immortallity
1 devour
2 erebos
1 ultimate price
2 bile blight
2 drown in sorrow
3 duress
3 dark betrayal

On my phone at work so trying to remeber build off top of my head think sanguine bond should be inhere.somwhere

The double gray merchant dam the lifelink creatures dealing double seems goodd to me it is a 5 drop but devotion is good in black just about everything permanent ihas 1bb or a combo like that
Otger possible cards or 1ofs i like
Lord of the void
And
Sech(w/e the black primodial) from gatecrash

First off, there really isn't much need to have a discussion about the most dominant deck in the format. It's good, if you have the cards, just go with the version putting up the best results these days.

Now, for the actual decisions you're looking at making, I still think if you're going to splash something, splashing green or white is a much more effective route than red. As much as I would like Rakdos something to be tier 1, you need the ability to remove enchantments and red just doesn't give that to you.

As for the "outside the box" cards you were referencing at the end, Abhorrent Overlord is a better option than Lord of the Void or the Primordial. If you have any meaningful devotion, it will make a bunch of harpies, then you can sac it to itself, reanimate with the whip and get even MORE harpies. Then again, this is hardly a new idea as Travis Woo and many others would've proposed it months ago.

Anywhom, I would just run the established list if you're going to run mono-black... but that's just me.

B/g is a no brainer but the scry is really what i wanted the added removal is great though

The white seems good bc of blood baron sideboard gods willing and the like
Rootborn on pack rat token :)
But is there anything in black to destroy enchantments ik the gods i can hopefully hit with my own god or if i have to use lily

I agree with TY, jamming in, cards to make it "unique" just takes away from the power of the deck. The deck has been run and tested by countless pros that put far more time in the game than any of us. I'd trust in their reasoning for the choices.

I will say one thing though. You can make meta dependent choices to strengthen the deck, this is where you're knowledge of what's being played in you're area comes in. If you see lots of UWx control then splashing green or white is probably okay for enchantment removal. If you see tons of aggro, then you may main deck bile blight. That's all on you though and nothing we say can help you really get a feel for you meta.

if you're worried about opposing gods, mono black usually doesn't have trouble with them too much, with the removal suite they run... gild can be an option after they're turned on...

so after some tweaking trying to figure out if i wanna cut heralds or not has anyone been using them w any success? it seems good and bad, the -1 life cuts out some of the undeworld draws i think atleast any opinion play monoblack tonight

i dont have access to nigthveils so what would i replace my 3 of heralds w/?
more removal?

if you don't have access to nightveils then lifebane zombe is a good choice for the deck, herald after that, it's still a 3/3 for three, but lifebane just fights the plan better.

what's your list look like now?

make sure you have extra lands... most people don't think about it, but underworld connections takes up one of your lands to draw so it basically reads pay B, and 1 life to draw a card. Also, with mutavaults you have to make sure you hit at least double black since you're not playing specter.

I tried 25 for a long time and basically settled on 26 because of this.

3 underworld 4 pack rat 4 grays 4 des demon 4 lifebane 3 heralds 2 devour 2 biles 1 ultimate price 4 thoughtseize 4 heros downfall 2 muta (trying to get more) 3 temples 20 swamps 1 nykthos something like that not at home atm

obviously you'd want the other muta's and another template. I liked running a 1 of nykthos, but a lot of lists don't run it at all anymore, so i guess it's personal taste.

it should be either lifebanes or herald's really, but not both, at least not in those qty's. You might try a 2/2 split or something, but the removal is just to important. Drop the herald's and come up an underworld connections and 2 devours or a devour/ultimate price.