Engineered Plague

As Engineered Plague enters, choose a creature type.
All creatures of the chosen type get -1/-1.

Skittering Skirge

Flying
When you cast a creature spell, sacrifice Skittering Skirge.

Eradicate

Exile target nonblack creature. Search its controller's graveyard, hand, and library for all cards with the same name as that creature and exile them. Then that player shuffles.

Dark Ritual

Stromgald Cabal

{T}, Pay 1 life: Counter target white spell.

Perish

Destroy all green creatures. They can't be regenerated.

Spawning Pool

Spawning Pool enters tapped.
{T}: Add {B}.
{1}{B}: Spawning Pool becomes a 1/1 black Skeleton creature with "{B}: Regenerate this creature" until end of turn. It's still a land. (If it regenerates, the next time it would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

Skittering Horror

When you cast a creature spell, sacrifice Skittering Horror.

Phyrexian Negator

Trample
Whenever Phyrexian Negator is dealt damage, sacrifice that many permanents.

Unmask

You may exile a black card from your hand rather than pay this spell's mana cost.
Target player reveals their hand. You choose a nonland card from it. That player discards that card.

Duress

Target opponent reveals their hand. You choose a noncreature, nonland card from it. That player discards that card.

Thrashing Wumpus

{B}: Thrashing Wumpus deals 1 damage to each creature and each player.

Vicious Hunger

Vicious Hunger deals 2 damage to target creature and you gain 2 life.

Massacre

If an opponent controls a Plains and you control a Swamp, you may cast this spell without paying its mana cost.
All creatures get -2/-2 until end of turn.

Yawgmoth's Will

Until end of turn, you may play lands and cast spells from your graveyard.
If a card would be put into your graveyard from anywhere this turn, exile that card instead.

Swamp

Persecute

Choose a color. Target player reveals their hand and discards all cards of that color.

Rishadan Port

Stupor

Target opponent discards a card at random, then discards a card.

Vampiric Tutor

Search your library for a card, then shuffle and put that card on top. You lose 2 life.