Night of Souls' Betrayal

Massacre Wurm

When this creature enters, creatures your opponents control get -2/-2 until end of turn.
Whenever a creature an opponent controls dies, that player loses 2 life.

Black Sun's Zenith

Put X -1/-1 counters on each creature. Shuffle Black Sun's Zenith into its owner's library.

Cower in Fear

Creatures your opponents control get -1/-1 until end of turn.

Nausea

All creatures get -1/-1 until end of turn.

Kaervek, the Spiteful

Tragic Slip

Target creature gets -1/-1 until end of turn.
Morbid — That creature gets -13/-13 until end of turn instead if a creature died this turn.

Make Obsolete

Maha, Its Feathers Night

Flying, trample
Ward—Discard a card.
Creatures your opponents control have base toughness 1.

Curse of Death's Hold

Enchant player
Creatures enchanted player controls get -1/-1.

Plague Mare

Plague Mare can't be blocked by white creatures.
When Plague Mare enters, creatures your opponents control get -1/-1 until end of turn.

Seeker's Folly

Choose one —
• Target opponent discards two cards.
• Creatures your opponents control get -1/-1 until end of turn.

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.

Stab

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

Toxic Deluge

As an additional cost to cast this spell, pay X life.
All creatures get -X/-X until end of turn.

Pestilence

At the beginning of the end step, if no creatures are on the battlefield, sacrifice Pestilence.
{B}: Pestilence deals 1 damage to each creature and each player.

Blood Artist

Whenever Blood Artist or another creature dies, target player loses 1 life and you gain 1 life.

Gruesome Realization

Choose one —
• You draw two cards and you lose 2 life.
• Creatures your opponents control get -1/-1 until end of turn.

Suffocating Fumes

Creatures your opponents control get -1/-1 until end of turn.
Cycling {2} ({2}, Discard this card: Draw a card.)