Demon of Catastrophes

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

Macabre Mockery

Put target creature card from an opponent's graveyard onto the battlefield under your control. It gets +2/+0 and gains haste until end of turn. Sacrifice it at the beginning of the next end step.

Claim the Firstborn

Gain control of target creature with mana value 3 or less until end of turn. Untap that creature. It gains haste until end of turn.

Ravenous Harpy

Flying
{1}, Sacrifice another creature: Put a +1/+1 counter on Ravenous Harpy.

Severed Strands

As an additional cost to cast this spell, sacrifice a creature.
You gain life equal to the sacrificed creature's toughness. Destroy target creature an opponent controls.

Thrill of Possibility

As an additional cost to cast this spell, discard a card.
Draw two cards.

Fabled Passage

{T}, Sacrifice Fabled Passage: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle. Then if you control four or more lands, untap that land.

Ritual of Soot

Destroy all creatures with mana value 3 or less.

Hijack

Gain control of target artifact or creature until end of turn. Untap it. It gains haste until end of turn.

Dragonskull Summit

Dragonskull Summit enters tapped unless you control a Swamp or a Mountain.
{T}: Add {B} or {R}.

Bloodfell Caves

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {B} or {R}.

Vraska, Swarm's Eminence

Whenever a creature you control with deathtouch deals damage to a player or planeswalker, put a +1/+1 counter on that creature.
−2: Create a 1/1 black Assassin creature token with deathtouch and "Whenever this creature deals damage to a planeswalker, destroy that planeswalker."

Village Rites

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

Reassembling Skeleton

{1}{B}: Return this card from your graveyard to the battlefield tapped.

Doomed Dissenter

When Doomed Dissenter dies, create a 2/2 black Zombie creature token.

Act of Treason

Gain control of target creature until end of turn. Untap that creature. It gains haste until end of turn. (It can attack and {T} this turn.)

Blood Crypt

({T}: Add {B} or {R}.)
As Blood Crypt enters, you may pay 2 life. If you don't, it enters tapped.

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.

Mountain

Command the Dreadhorde

Choose any number of target creature and/or planeswalker cards in graveyards. Command the Dreadhorde deals damage to you equal to the total mana value of those cards. Put them onto the battlefield under your control.