Ok, it took me a while to realise this was a deck intended for Multiplayer. I was very sceptical when viewing it from a 1v1 modern perspective. Maybe clarify in the description as well as the tag, as I can see im not the first to be confused.

I dont know the multiplayer format very well, but i would only assume that Tron, Storm and KCI are extremely strong. I get that this is a budget deck, not made for combatting these giants. But if your meta is anything like my Commander playgroup, players will upgrade their decks little by little over time. So Knowing what to upgrade yourself when the time comes is wise.

Against Tron you can simply play more landdestruction. Adding 4x Ghost Quarter does not hurt your mana too bad. Artifact destruction is not something we have access to in mono-black (at least not in modern), but you could consider Lux Cannon. It has synergy with the proliferate cards, and its great against a deck like Tron, or artifact-based combo (KCI).

Your deck is pretty weak against degenerate combo decks, storm being the one I know best from 1v1 modern. There are tons of ways for black to screw with an opponents combos though. Hand-attack, deck attack and graveyard hate. Duress gets the job done against most decks. Memoricide gets combopieces even before they reach their owners hand, while maintaining the very important Mirrodin Vibes. This should help you hose the comboplayer enough that you can focus on the other two. Notably with Duress, you only have to slow them down enough that you can kill them with poison.

Dredge is a pain in the behind, so Relic of Progenitus or Nihil Spellbomb is real nice.

Nice! I like this deck, and good job with it. What worries me, though, is that you’re playing 20 lands with 6 and 5 mana creatures. I don’t mean to sound criticising or anything, but I think you might want a few more lands in this to make it more consistent. I think the most beneficial fix here would be to take out the Banshees and add 2 more lands, because 22 lands with a curve that tops out at 5 is okay, but I also see why you would want to keep them in the deck. Anyway, just something to think about. Other than that, it looks pretty good. +1 from me

I would suggest these revisions to the mainboard: +4 Phyrexian Crusader -4 Scar

-2 Swamp +2 Memorial to Folly

-4 Swamp +4 Inkmoth Nexus (I know this is a budget deck, but I believe this will receive a reprint soon, and while 1-2 copies is expensive, it won't break the wallet)

-2 Septic Rats +2 Ichorclaw Myr

-2 Blowfly Infestation +2 Nest of Scarabs

+1 Skithiryx, the Blight Dragon -1 Virulent Wound