Lockjaw Snapper

Wither (This deals damage to creatures in the form of -1/-1 counters.)
When Lockjaw Snapper dies, put a -1/-1 counter on each creature with a -1/-1 counter on it.

Blight Sickle

Equipped creature gets +1/+0 and has wither. (It deals damage to creatures in the form of -1/-1 counters.)
Equip {2}

Incremental Blight

Put a -1/-1 counter on target creature, two -1/-1 counters on another target creature, and three -1/-1 counters on a third target creature.

Mountain

Commander's Sphere

{T}: Add one mana of any color in your commander's color identity.
Sacrifice Commander's Sphere: Draw a card.

Mizzium Mortars

Mizzium Mortars deals 4 damage to target creature you don't control.
Overload {3}{R}{R}{R} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Carnifex Demon

Flying
Carnifex Demon enters with two -1/-1 counters on it.
{B}, Remove a -1/-1 counter from Carnifex Demon: Put a -1/-1 counter on each other creature.

Hateflayer

Wither (This deals damage to creatures in the form of -1/-1 counters.)
{2}{R}, {Q}: Hateflayer deals damage equal to its power to any target. ({Q} is the untap symbol.)

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Profane Memento

Whenever a creature card is put into an opponent's graveyard from anywhere, you gain 1 life.

Harbinger of Night

At the beginning of your upkeep, put a -1/-1 counter on each creature.

Midnight Banshee

Wither (This deals damage to creatures in the form of -1/-1 counters.)
At the beginning of your upkeep, put a -1/-1 counter on each nonblack creature.

Blur of Blades

Put a -1/-1 counter on target creature. Blur of Blades deals 2 damage to that creature's controller.

Rakdos Guildgate

This land enters tapped.
{T}: Add {B} or {R}.

Skinrender

When Skinrender enters, put three -1/-1 counters on target creature.

Swamp

Temple of the False God

{T}: Add {C}{C}. Activate only if you control five or more lands.

The Scorpion God

Whenever a creature with a -1/-1 counter on it dies, draw a card.
{1}{B}{R}: Put a -1/-1 counter on another target creature.
When The Scorpion God dies, return it to its owner's hand at the beginning of the next end step.

Hellrider

Haste
Whenever a creature you control attacks, Hellrider deals 1 damage to the player or planeswalker it's attacking.

Cryptborn Horror

Trample
Cryptborn Horror enters with X +1/+1 counters on it, where X is the total life lost by your opponents this turn.

Rakdos Carnarium

Rakdos Carnarium enters tapped.
When Rakdos Carnarium enters, return a land you control to its owner's hand.
{T}: Add {B}{R}.

Rakdos Cluestone

{T}: Add {B} or {R}.
{B}{R}, {T}, Sacrifice Rakdos Cluestone: Draw a card.

Ribbons

Aftermath (Cast this spell only from your graveyard. Then exile it.)
Each opponent loses X life.

Cut // Ribbons

Solemn Simulacrum

When this creature enters, you may search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.
When this creature dies, you may draw a card.