Altar's Reap

As an additional cost to cast this spell, sacrifice a creature.
Draw two cards.

Plaguecrafter

When Plaguecrafter enters, each player sacrifices a creature or planeswalker of their choice. Each player who can't discards a card.

Eternal Taskmaster

Eternal Taskmaster enters tapped.
Whenever Eternal Taskmaster attacks, you may pay {2}{B}. If you do, return target creature card from your graveyard to your hand.

Demon of Catastrophes

As an additional cost to cast this spell, sacrifice a creature.
Flying, trample

Dusk Legion Zealot

When Dusk Legion Zealot enters, you draw a card and you lose 1 life.

Audacious Thief

Whenever Audacious Thief attacks, you draw a card and you lose 1 life.

Black Cat

When Black Cat dies, target opponent discards a card at random.

Defile

Target creature gets -1/-1 until end of turn for each Swamp you control.

Murder

Languish

All creatures get -4/-4 until end of turn.

Ogre Slumlord

Whenever another nontoken creature dies, you may create a 1/1 black Rat creature token.
Rats you control have deathtouch.

Sparring Construct

When Sparring Construct dies, put a +1/+1 counter on target creature you control.

Disfigure

Target creature gets -2/-2 until end of turn.

Typhoid Rats

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)

Serrated Scorpion

When Serrated Scorpion dies, it deals 2 damage to each opponent and you gain 2 life.

Phyrexian Rager

When Phyrexian Rager enters, you draw a card and you lose 1 life.

Gruesome Menagerie

Choose a creature card with mana value 1 in your graveyard, then do the same for creature cards with mana value 2 and 3. Return those cards to the battlefield.

Ayara, First of Locthwain

Whenever Ayara, First of Locthwain or another black creature you control enters, each opponent loses 1 life and you gain 1 life.
{T}, Sacrifice another black creature: Draw a card.

Tendrils of Corruption

Tendrils of Corruption deals X damage to target creature and you gain X life, where X is the number of Swamps you control.

Ravenous Chupacabra

When Ravenous Chupacabra enters, destroy target creature an opponent controls.

Swamp

Piper of the Swarm

Rats you control have menace.
{1}{B}, {T}: Create a 1/1 black Rat creature token.
{2}{B}{B}, {T}, Sacrifice three Rats: Gain control of target creature.

Falkenrath Noble

Flying
Whenever Falkenrath Noble or another creature dies, target player loses 1 life and you gain 1 life.

Gravedigger

When Gravedigger enters, you may return target creature card from your graveyard to your hand.