Seriously, Ross?? Another Smallpox deck? I think you might have a problem.
No, I don't have a problem. I have everything completely under control. I can quit any time I want.
So you're saying if I leave a playset of Smallpox on the table and turn my back, there won't be a full 75 when I turn back around?
...okay, maybe you have a point. But just give me this last one. It's Legacy and has a lot of sweet things going for it.
I'm looking forward to next week's Smallpox variant already.
Can't stop, won't stop. Smallpox is awesome, but the Legacy variant of the deck, typically mono-black, has some issues, all of which are conveniently solved by the green splash.
First, you can't answer non-creature, non-land permanents once they enter the battlefield. Enter Abrupt Decay. You don't tag Jace, the Mind Sculptor, but with your strong resource denial plan and creature-lands, Jace, the Mind Sculptor shouldn't be too big of an issue.
Second, the deck lacks any true sources of card advantage. Smallpox means Dark Confidant is a no-go and things like Phyrexian Arena just won't cut it. Life from the Loam may only return lands, but in Legacy those lands can be Barren Moor, Cabal Pit, Dark Depths, Wasteland, or The Tabernacle at Pendrell Vale. The extra cards also supercharge your Liliana of the Veils, letting you activate her +1 with impunity to keep your opponent low on cards.
And third, you don't have much of a clock, the classic Pox folly. Well, last time I checked, 20/20 Flying creatures are a good clock. Dark Depths plus Thespian's Stage is what allowed Lands to enter the top tier of Legacy by giving the deck a combo finish, and it should work in the same role here.
And finally, the deck has an issue with executing its gameplan in time. Legacy decks are explosive and resilient enough to withstand a discard spell or two, establish a battlefield, and blank your ensuing discard spells. Mox Diamond is a great accelerant that wouldn't be playable without Life from the Loam since you're so tight on resources otherwise.
Four problems and they're all solved with one color. When did green become so good?