Anyways, black deck, here's the reasons for what is in it:

Sanguine Bond - Core of the deck. Gain life, hurt opponent. Deck focuses on cards that gain life AND hurt opponent, thus doubling the hurt when SB is in play. Sanguine Bond is expensive, so deck needs to survive in some capacity until it can be brought to bear.

Corrupt - This is almost a win condition. If you can cast it with a SB out, on turn 6, opponent loses 12 life, you can 6.

Tavern Swindler - a normally stupid card, but because of how it is worded (you gain 6 life), it's a coin toss to either lose 3 life or gain 12 net life (with an SB in play)

Trading Post - Discard a card to gain 4 life. Also makes goats for various effects.

Festering Newt - a dangerous creature all by itself on turn one. Also, it's ability to apply it's -1/-1 to target creature can get rid of mana druids, etc.

Tenacious Dead - cheap blocker against non-trample.

Quag Sickness - removal, great in mono-black for killing about anything.

Crypt Incursion - 3 life / dead creature is awesome. With SB, that's 3 life / 3 damage.

Killing Glare - Removal

Doom Blade - Removal

Bubbling Cauldron - it's cheap and the combo with newt is awesome with SB out. Otherwise, goats from Trading Post will do.

Liliana of the Dark Realms - Win condition for deck is expensive. Liliana means you can get there predictably without becoming mana starved around 4 lands. You need 6 to make the deck win. 2nd ability is nice removal. ultimate has little use.

Thrull Parasite - 1 drop extort creature.

Nightmare - To round out my 6 drop spot. Should probably replace with another corrupt, as they are same cost. Mono black does make some tough nightmares though.

Daggerdrome Imp - 2 drop lifelink flying isn't bad. without enchantments, he's weak.

Dark Prophecy - An experiment in whether deck cycling is good or whether my creatures are dying enough for it to make a difference.