Gray Merchant of Asphodel

When Gray Merchant of Asphodel enters the battlefield, each opponent loses X life, where X is your devotion to black. You gain life equal to the life lost this way. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)

Swamp

Unearth

Return target creature card with mana value 3 or less from your graveyard to the battlefield.
Cycling {2} ({2}, Discard this card: Draw a card.)

Phyrexian Obliterator

Trample
Whenever a source deals damage to Phyrexian Obliterator, that source's controller sacrifices that many permanents.

Geralf's Messenger

Geralf's Messenger enters the battlefield tapped.
When Geralf's Messenger enters the battlefield, target opponent loses 2 life.
Undying (When this creature dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)

Not Dead After All

Until end of turn, target creature you control gains "When this creature dies, return it to the battlefield tapped under its owner's control, then create a Wicked Role token attached to it." (Enchanted creature gets +1/+1. When this Aura is put into a graveyard, each opponent loses 1 life.)

Archfiend's Vessel

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
When Archfiend's Vessel enters the battlefield, if it entered from your graveyard or you cast it from your graveyard, exile it. If you do, create a 5/5 black Demon creature token with flying.

Hopeless Nightmare

When Hopeless Nightmare enters the battlefield, each opponent discards a card and loses 2 life.
When Hopeless Nightmare is put into a graveyard from the battlefield, scry 2.
{2}{B}: Sacrifice Hopeless Nightmare.

Gifted Aetherborn

Gatekeeper of Malakir

Kicker {B} (You may pay an additional {B} as you cast this spell.)
When Gatekeeper of Malakir enters the battlefield, if it was kicked, target player sacrifices a creature.

Nighthawk Scavenger

Flying, deathtouch, lifelink
Nighthawk Scavenger's power is equal to 1 plus the number of card types among cards in your opponents' graveyards.