NBonezM

Or perhaps play Enchroach? Really stick it to their manabase before it can even get started haha

Maybe it's just me but Deathcloud seems kinda out of place because you're either trying to land a huge bomb early or slowly draining the hope for their deck. In both cases, having you sacrifice just as many things is counterproductive.
In other words, Deathcloud is the last thing in this deck I'd want to play. Not that it's bad, it's a very terrifying card, but everything else in your deck does the same exact thing but better (either it's cheaper mana or simply more powerful). Maybe consider adding a few Nether Traitors as another sac outlet for Culling the Weak, Smallpox, and big Pox rather than just Bloodghast.
Overall it's an outstanding deck and perfectly epitomizes Black's slogan "Victory at any Cost."

In response of Dharr16, Path to Exile is an extremely efficient card from a mana perspective. However I wouldn't want to see more than 1 in a game because being behind will lose me the game. I can handle being down 1 land but when they have 6 or 7 lands and I only have 4 or 5 I'm at a clear disadvantage (even if I have exiled 2 of their creatures). I think 2 is the right number for this deck.
kmk888, I'm really reluctant to switch FC for Bile Blight for one primary reason: It costs a additional mana. It is true that Bile Blight has a much larger target range than Funeral Charm and has the potential bonus of killing a wave of tokens or something but at the same time I would hate to be staring at a creatureless opponent with a BB in hand while the FC can at least be thrown at them if it doesn't kill something. I think I'll have to playtest both and see if the extra mana gets in the way or not. It's really a meta/game specific question so we'll see.
Thanks again for the ideas!

Thanks for the detailed response! I had totally forgotten about Batterskull, definitely a contender for the slot. At this point I think I'll keep the Blood Barons in just because I have them.
The Funeral Charm was first added because it's an instant speed discard effect. When I first added it I was considering going heavier into the discard aspect but have eased back slightly. The reason I've kept it in is because it's an extremely efficient removal spell for Modern powerhouses (i.e. Snappy, Clique, Confidant and rarer bombs like Thalia which could cause issues for for a deck like this).
But having thought about it, I'm not as fond of it as I was. What should I consider playing instead? Btw I'm avoiding more Geth's V in the main because Zoo has been coming back with a vengeance and it's largely useless against that deck and decks like it.

Magic Community!
I'm trying to make this Modern playable and tbh I HATE the High Priests in the deck and am not a particular fan of Blood Baron.
What can a put in their place???

Yeah, I changed it slightly to add 3 Birds of Paradise and 2 Browbeats. I think they're pretty good switches and brings my curve down a bit too.
Thanks for the comment! :)

I personally don't like the Liliana of the Dark Realms, I think this deck would be better to just have 4 Dragons and Demons.
That being said, this deck looks pretty solid to me.

THIS IS A MODERN DECK!
Everything you suggested (except fabricate which is too slow for this deck) is only playable in Legacy.
And you play Myr Superion with the Heartless Summoning. Whether that will ever actually happen with only 2 is a different matter.
Remand is basically a Timewalk in Modern so please do continue to play them.

Razka, I agree it would be powerful but that would push this deck into the Legacy list rather than Modern.
That being said this deck looks really well done but I fell like 24 lands is too many for this deck's curve, 20-22 would be a better number I think. Shimmer Myr is a great addition I hadn't considered (referring to Heartless Summoning).
I can't really think of any way to make this better without being really conditional.
Again, Well done!

Is there a reason you're playing Nightmare Lash vs. Lashwrithe? I think the latter is better.
I would also play Thoughtpicker Witch instead of the Beetle. Every turn you can look at the top 2 cards of their library and FORCE them to have a crap draw. Seems pretty powerful in this deck with everything else. Or you could consider Bloodthrone Vampire because, to me, you don't have enough sac outlets.
On that note, you may want to take out the Mindcrank for Either of them because it seems kinda out of place.
Hope this is somewhat helpful!

For those who don't want to read the whole description, I don't like the Balefire Lieges. What should I play instead of them? And any suggestions for the sideboard???
Thanks a ton!

I like some of the stuff going on here and some of it I'm not so such of a fan.
Duskmantle Seer, in my opinion, is the most out of place here. A card like this really needs to have the deck built around to take full advantage of the extra draw/life loss. As of now you have an ACMC of 1.96 ~ 2 but among your spells the average is above 3 so you could be taking hefty chunks of life loss that you may not be able to afford (especially because you don't have any lifegain). Blood Scrivener seems odd to me here: you don't have enough in the deck to be expecting to see one every game and on top of that I recently made a BUG list starring Duskmantle Seer; If you wanted to take a minute to look it over and give any suggestions that would be great.

I like the inclusion of Thassa but think the Master of Waves is less effective than it could be if you played some things like Nightveil Specter rather than Ubul Sar Gatekeeps. Also Beetleform Mage is a good addition because it's a card that demands an answer or the game can be over quickly and will draw removal away from other targets you'd rather hold on to.
Ashiok and Thoughtseize are two cards you may fit in well in this deck ( But I would think Ashiok moreso than Thoughtseize). Sylvan Caryatid may also be useful for getting Vraska, Jace or some big creatures out a turn early too.

If you want to talk metagame I'd be more than happy to but I didn't want to write too long of a comment.
Hope this is somewhat helpful.

That's true, if I end up making this a Legacy deck I'll give it some serious thought. Thanks!

Okay I've been thinking about this for a little while, but I'd like to start off by saying I'm not an expert in Legacy gameplay. I think you should have 3 Torpor Orb and 3 Illusionary Mask's main board and 1 of each in your side. That way, someone can't Slaughter Games or Surgical Extration your sole win condition. I would suggest dropping 1 avatar of Discard and 1 Mountain for the Illusionary masks.
The diregraf ghouls seem like filler to me so I think you should switch tem out for 2 Treacherous Pit Dwellers. It's a very solid 4/3 for 2 mana whose ETB ability isn't likely to be damaging to you if you cast him before the Torpor Orb. Even if he gets lightning Bolted or something the turn you play him and they get a 5/4, it's not that big of a deal because it's one of the smaller creatures in your deck haha. That's about all I can recommend for the main board.
Sideboards are trickier because it has a lot to so with what types of decks are played in your area. There are three types that are easy to deal with in B/R: graveyard based, storm-style deck, and creature based (which you already handle pretty well). There are many things that are good against graveyards like Nihil Spellbomb and Faerie Macabre. For storm decks there's good old Trinisphere. Decks that run Force of will I can see as being annoying so a Slaughter Games or two wouldn't be bad along with Pyroblast and Red Elemental Blast. Blood moon may also be a good card to grab with Death Wish.
Hope this helps!

You have too many creatures, the deck needs to be more focused. Obviously dual lands are a good call.
4 Simian Spiritguides and 4 Chrome Mox are a must so that you can abuse the Orb Turn 1. Diabolical Tutor is too expensive (mana wise) Death Wish would be better because you can search for the card you need to beat your opponent's deck AND you don't have to reveal it.
Hunted Dragon and Shivan Whompus are te weakest cards in the deck, in my opinion and should be taken out

Take a look at this deck for ideas. Basically it wins by turn 6 or gets mana flooded.
Tajic and Frontline Medic are usually too slow so I think I'm going to take them out.
http://www.mtgdeckbuilder.net/Decks/ViewDeck/759014

I hate to burst your bubble, but you're not dealing damage, you're causing life loss. HUGE difference: damage can be prevented but life loss can't. I think you should play doom blade over Murder and side it out against other black decks. Other than that I looks good as long as it doesn't get overrun by Gruul Aggro or something

The main board looks pretty good. I would play Plasm Capture over Mystic Genesis though (I know you want the token to populate it but 5 is alot for a counterspell). In the sideboard I don't think you need 1 Elvish Mystic (1 will never really be helpful), 1 Voracious Wurm (you don't have THAT much life gain that it could be relied upon) and the same goes for the Angelic Accord. Savage Summoning could be good to add (flashing in a Progenitor Mimic or Aetherling would be brutal) and Imposing Soveriegn (to shut down the haste in Red and Gruul Aggro).

I can see the single Disentomb being useful though to get back a late game Varolz or something to keep the pressure on/ scavenge and win.

Haha things don't get "accidentally mulched", they're Mulched on purpose! This deck wants to load up the graveyard quickly. I could be wrong but Scavenging Ooze wouldn't target it's own graveyard; rather, it would target the opponent's. Shutting down everything from the mirror match to reanimator to flashback to Varolz. Or even if they don't utilize their graveyard you can still grab creatures out of it and make a huge Grizzly Bear.