Really late prerelease detailed post. EDIT: By which I mean, this is about last week.
I went 3-2-1 with a B/G deck that I found pretty fun. Though I did lose to color screw a few times, most of my losses were pretty close.
Black cards:
1x Miasmic Mummy - Creature - 1B - Never used it to get a graveyard card into the graveyard, but it was decent.
2x Splendid Agony - Instant - 2B - Good and versatile removal. It was great using it on opposing Exemplar of Strengths and such.
1x Cartouche of Ambition - Enchantment - 2B - This was pretty good, both as removal and for lifelink.
1x Unburden - Sorcery - 1BB - I never actually cast this, I only cycled it.
1x Bone Picker - Creature - 3B - I got the cost reduction a few times, but not on turn 3 or before. This was really useful with the ground getting clogged.
1x Pitiless Vizier - Creature - 3B - I was able to give it indestructible once, and it was otherwise a nice attacker.
1x Archfiend of Ifnir - Creature - 3BB - I never got the cycling trigger, and this usually got killed or exiled before I attacked with it. I had to cycle it a few times due to mana screw.
1x Liliana's Mastery - Enchantment - 3BB - I never got this and Miasmic Mummy out at the same time. Still, two 3/3 zombies were decent enough.
1x Final Reward - Instant - 4B - Only got to cast this once, but it was nice.
Green cards:
1x Exemplar of Strength - Creature - 1G - This guy was a good attacker.
1x Initiate's Companion - Creature - 1G - A better attacker than I expected, and it provided mana acceleration.
2x Cartouche of Strength - Enchantment - 2G - Surprisingly great removal.
1x Defiant Greatmaw - Creature - 2G - I got this out as a 4/5 more than I expected, and it was pretty good. I used the counter removing ability once.
1x Pouncing Cheetah - Creature - 2G - This was pretty good.
1x Watchful Naga - Creature - 2G - This usually went on a sacrificial attack to draw a card, and it was fine as that.
1x Giant Spider - Creature - 3G - Way better in this environment than I would have ever guessed.
1x Quarry Hauler - Creature - 3G - I once used this to kill a Channeler Initiate. That was nice.
1x Vizier of the Menagerie - Creature - 3G - The first time I used this, I got to flash out Pouncing Cheetah during my opponent's turn. This was a really good card.
1x Greater Sandwurm - Creature - 5GG - I cycled this most of the time, but I did bring it out a few times, and it was good then.
1x Sandwurm Convergence - Enchantment - 6GG - I got this out two times, and though it was slow going, I won both games with my opponent barely able to do anything about it. So yeah, good card.
Multicolored card:
1x Destined // Lead - Instant/Sorcery - 1B / 3G - Destined was alright. There were times I could have cast Lead, including one where it could have let me win the game, but I forgot about it, only to look at it sticking out of my graveyard right after and smack myself.
Lands:
7x Swamp
9x Forest
1x Fetid Pools - I never played this, only cycling it. But that means I didn't need a land then, so that's exactly the purpose.
In retrospect, I should have included Soulstinger, likely swapping out Unburden. There were also mulligans I probably shouldn't have done, acknowledging the slower speed of the format.
