Hi, greenbean98. I downloaded this deck and loaded it into Cockatrice last night, and have played four one-on-one games against it with two of my Commander decks that are pretty good, just to test things out. I have a couple of observations for you. I hope you take them in the helpful intention they are provided. I *do* understand that this deck is under construction.
First, this deck is very light on mana. I would suggest taking out 2 or 3 of your least-liked creatures and adding more land, and/or some mana ramp like
Dark Ritual,
Wild Growth,
Sol Ring and
Golgari Signet. Since the deck is full of small, low-casting cost creatures, I think you need to get them into play rapidly to keep up with your opponent, and in the games I played it did not draw land fast enough to compete.
Second, your lack of big stompy creatures (5/4 flying
Butcher of Malakir is the biggest I've found) is likely to be a major problem when other Commander decks start bringing out their big guns. If this were my deck, I'd add some black Dragons and / or big green Beasts, or something similar. A
Fog or
Constant Mists would slow down your opponents' attacks.
Third, you're lacking one of black's great strengths- instants and sorceries to destroy enemy creatures.
Murder,
Diabolic Edict,
Annihilate or good old
Terror would help keep opposing creatures off of you.
Fourth and finally, you have little to no protection against flyers. One of the decks I played against this one has Dragons and generates dragon counters, and the other one generates
Angel counters. They simply flew over your deck and destroyed it.
I know that Commander is meant to be multiplayer, but a good way to test a deck you're working on is to load it into Cockatrice and play it against other decks downloaded from here. If you label your Commander as such, DeckStats will give you card suggestions, as will another site that might not be cool to name in comments here.
Best of luck with your deck!