You have to manually enter each card into their system, which was simple, but I did notice some preview images were off (like showing Japanese versions instead of English ones)
While it is probably good enough in a deck that is built on the theme of +1/+1 counters, outside of this very specific archetype, adding a single +1/+1 counter to a creature just isn't enough value (even at instant speed) to make me add another tapped land to my deck, especially considering that green already has five MDFCs that I really want to be playing
A good reason for going mono-black is that black can cover almost all bases well (except artifact destruction)
Scrawling Crawler Scrawling Crawler looks like the child of Howling Mine and Sheoldred, the Apocalypse
Sword Coast Sailor and Raised by Giants are two options that broaden your access to other colors and make for some quick kills via commander damage.
He can however take some Survivor cards to tip the odds in his favour or Guardian cards to heal and negate some damage