I almost feel that red is not needed here. if you are looking for reach with Lightning Bolt maybe run Bump in the Night or just run it anyway with red you can pay flashback. if it is for removal try Disfigure not quite as powerful or versatile, but it would get you out of having to splash an extra color. As far as sideboard goes, I would suggest maybe Black Sun's Zenith instead of Pyroclasm. These are simply suggestions that I personally think would be better than splashing red. Also I couldn't imagine playing Smallpox without running Bloodghast. He is in the top 5 of my favorite cards printed so there is a bit of bias to that. Death Cloud may be a nice 1-2 of in this deck as well.

Thanks for the advice! I agree with you about red - I'm actually working on a new BW build. I tried Mardu before and I think it's basically a different, more aggressive deck entirely. That being said, Disfigure feels kinda sad in comparison to Lightning Bolt, but that's without any testing - I'm sure it kills more than I think it does.

As far as Bloodghast goes, I've tried to use him before. He's good if you're the aggro deck in the matchup... but there are a lot of aggro decks running around Modern and I always seem to need a blocker. Also, half the time the creatures in modern can just profitably block him anyway and I end up with a ghast just sitting there. Overall I haven't been too impressed. If I was dredging more, it would likely be a different story.

I used to run a BG Death Cloud build and loved it, but wanted something quicker than a ramp strategy. Outside of a ramp strategy death cloud doesn't seem as good. I'll give it a try though.

Thanks for the help!

I would say that Lightning Bolt is better than Disfigure also, but splashing just for it could cause more problems, maybe. Murderous Cut or Unmake might be another decent alternative. As far as Bloodghast goes, he can be aggro, but He gives you another non wasted discard aside from Lingering Souls if you cast Smallpox or use Liliana of the Veil 's + ability. His utility, IMO, is less for his body so much as its synergy with other cards. Different play styles make a cards usefulness different though. He works wonders for me, but may not for you.

http://tappedout.net/mtg-decks/mono-black-post-3/

Here's a budget build of pox/cloud of mine that I have been having a lot of fun with. It isnt the greatest deck on the planet, but I hear a lot of groaning when my opponents at FNM find out that they have to play against it. Overall, I am a big advocate of playing the cards you like. to hell if it is a top 8 worthy build. thats just me though. best of luck trimming things down!