Torment of Venom

Put three -1/-1 counters on target creature. Its controller loses 3 life unless they sacrifice another nonland permanent of their choice or discard a card.

Ritual of Soot

Destroy all creatures with mana value 3 or less.

Endemic Plague

As an additional cost to cast this spell, sacrifice a creature.
Destroy all creatures that share a creature type with the sacrificed creature. They can't be regenerated.

Mephitic Vapors

All creatures get -1/-1 until end of turn.
Surveil 2. (Look at the top two cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)

Lethal Vapors

Whenever a creature enters, destroy it.
{0}: Destroy this enchantment. You skip your next turn. Any player may activate this ability.

Cinderbones

Wither (This deals damage to creatures in the form of -1/-1 counters.)
{1}{B}: Regenerate this creature.

Cinder Barrens

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

Tormented Soul

This creature can't block and can't be blocked.

Ignorant Bliss

Exile all cards from your hand face down. At the beginning of the next end step, return those cards to your hand, then draw a card.

Pendrell Mists

All creatures have "At the beginning of your upkeep, sacrifice this creature unless you pay {1}."

Filter Out

Return all noncreature, nonland permanents to their owners' hands.

Wall of Vapor

Defender (This creature can't attack.)
Prevent all damage that would be dealt to this creature by creatures it's blocking.

Smog Elemental

Flying
Creatures with flying your opponents control get -1/-1.

Cinderhaze Wretch

{T}: Target player discards a card. Activate only during your turn.
Put a -1/-1 counter on this creature: Untap this creature.

Asphyxiate

Swamp

Graven Cairns

{T}: Add {C}.
{B/R}, {T}: Add {B}{B}, {B}{R}, or {R}{R}.

Jund Panorama

{T}: Add {C}.
{1}, {T}, Sacrifice this land: Search your library for a basic Swamp, Mountain, or Forest card, put it onto the battlefield tapped, then shuffle.

Miasmic Mummy

When this creature enters, each player discards a card.

Grim Affliction

Put a -1/-1 counter on target creature, then proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Ash Barrens

{T}: Add {C}.
Basic landcycling {1} ({1}, Discard this card: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.)

Snuff Out

If you control a Swamp, you may pay 4 life rather than pay this spell's mana cost.
Destroy target nonblack creature. It can't be regenerated.

Necrogen Mists

At the beginning of each player's upkeep, that player discards a card.

Breathe Your Last

Destroy target creature or planeswalker. You gain 1 life for each of its colors.

Chain of Smog

Target player discards two cards. That player may copy this spell and may choose a new target for that copy.

Toxic Stench

Target nonblack creature gets -1/-1 until end of turn.
Threshold — If seven or more cards are in your graveyard, instead destroy that creature. It can't be regenerated.

Nausea

All creatures 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.)

Marchesa, Dealer of Death

Whenever you commit a crime, you may pay {1}. If you do, look at the top two cards of your library. Put one of them into your hand and the other into your graveyard. (Targeting opponents, anything they control, and/or cards in their graveyards is a crime.)

Smokespew Invoker

{7}{B}: Target creature gets -3/-3 until end of turn.

Darkblast

Target creature gets -1/-1 until end of turn.
Dredge 3 (If you would draw a card, you may mill three cards instead. If you do, return this card from your graveyard to your hand.)

Creeping Tar Pit

This land enters tapped.
{T}: Add {U} or {B}.
{1}{U}{B}: This land becomes a 3/2 blue and black Elemental creature until end of turn and can't be blocked this turn. It's still a land.

Lingering Death

Enchant creature
At the beginning of the end step of enchanted creature's controller, that player sacrifices that creature.

Oboro, Palace in the Clouds

{T}: Add {U}.
{1}: Return Oboro to its owner's hand.

Infectious Host

When this creature dies, target player loses 2 life.

Unexplained Disappearance

Return target creature to its owner's hand.
Surveil 1. (Look at the top card of your library. You may put that card into your graveyard.)

Island

Chimney Imp

Flying
When this creature dies, target opponent puts a card from their hand on top of their library.

Die Young

Choose target creature. You get {E}{E} (two energy counters), then you may pay any amount of {E}. The creature gets -1/-1 until end of turn for each {E} paid this way.

Death Cloud

Each player loses X life, discards X cards, sacrifices X creatures of their choice, then sacrifices X lands of their choice.

Polluted Delta

{T}, Pay 1 life, Sacrifice this land: Search your library for an Island or Swamp card, put it onto the battlefield, then shuffle.

Smoldering Marsh

({T}: Add {B} or {R}.)
This land enters tapped unless you control two or more basic lands.

Chain of Vapor

Return target nonland permanent to its owner's hand. Then that permanent's controller may sacrifice a land of their choice. If the player does, they may copy this spell and may choose a new target for that copy.

Necrogen Scudder

Flying
When this creature enters, you lose 3 life.

Noxious Vapors

Each player reveals their hand, chooses one card of each color from it, then discards all other nonland cards.

Consuming Vapors

Target player sacrifices a creature of their choice. You gain life equal to that creature's toughness.
Rebound (If you cast this spell from your hand, exile it as it resolves. At the beginning of your next upkeep, you may cast this card from exile without paying its mana cost.)

Hissing Miasma

Whenever a creature attacks you, its controller loses 1 life.

Psychic Miasma

Target player discards a card. If a land card is discarded this way, return Psychic Miasma to its owner's hand.

Light 'Em Up

Casualty 2 (As you cast this spell, you may sacrifice a creature with power 2 or greater. When you do, copy this spell and you may choose a new target for the copy.)
Light 'Em Up deals 2 damage to target creature or planeswalker.

Moment of Craving

Target creature gets -2/-2 until end of turn. You gain 2 life.

Cinder Marsh

{T}: Add {C}.
{T}: Add {B} or {R}. This land doesn't untap during your next untap step.

Paradox Haze

Enchant player
At the beginning of enchanted player's first upkeep each turn, that player gets an additional upkeep step after this step.

Smoke

Players can't untap more than one creature during their untap steps.

Suffocation

Cast this spell only if you were dealt damage this turn by a red instant or sorcery spell.
Suffocation deals 4 damage to the controller of the last red instant or sorcery spell that dealt damage to you this turn.
Draw a card at the beginning of the next turn's upkeep.

Cloudkill

All creatures get -X/-X until end of turn, where X is the greatest mana value of a commander you own on the battlefield or in the command zone.

Seething Landscape

{T}: Add {C}.
{T}, Sacrifice this land: Search your library for a basic Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle.
Cycling {U}{B}{R} ({U}{B}{R}, Discard this card: Draw a card.)

Pestilent Haze

Choose one —
• All creatures get -2/-2 until end of turn.
• Remove two loyalty counters from each planeswalker.

Caustic Tar

Enchant land
Enchanted land has "{T}: Target player loses 3 life."

Succumb to Temptation

Stench of Decay

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

Learn from the Past

Target player shuffles their graveyard into their library.
Draw a card.

Bone to Ash

Counter target creature spell.
Draw a card.

Halls of Mist

Cumulative upkeep {1} (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
Creatures that attacked during their controller's last turn can't attack.

Smoldering Tar

At the beginning of your upkeep, target player loses 1 life.
Sacrifice this enchantment: It deals 4 damage to target creature. Activate only as a sorcery.

Ogre Menial

Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
{R}: This creature gets +1/+0 until end of turn.

Evolving Wilds

{T}, Sacrifice this land: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Horobi's Whisper

If you control a Swamp, destroy target nonblack creature.
Splice onto Arcane—Exile four cards from your graveyard. (As you cast an Arcane spell, you may reveal this card from your hand and pay its splice cost. If you do, add this card's effects to that spell.)

Smokestack

At the beginning of your upkeep, you may put a soot counter on this artifact.
At the beginning of each player's upkeep, that player sacrifices a permanent of their choice for each soot counter on this artifact.

Rising Miasma

All creatures get -2/-2 until end of turn.
Awaken 3—{5}{B}{B} (If you cast this spell for {5}{B}{B}, also put three +1/+1 counters on target land you control and it becomes a 0/0 Elemental creature with haste. It's still a land.)

Tar Fiend

Devour 2 (As this creature enters, you may sacrifice any number of creatures. It enters with twice that many +1/+1 counters on it.)
When this creature enters, target player discards a card for each creature it devoured.

Peppersmoke

Target creature gets -1/-1 until end of turn. If you control a Faerie, draw a card.

Necrogen Censer

This artifact enters with two charge counters on it.
{T}, Remove a charge counter from this artifact: Target player loses 2 life.

Fatal Fumes

Target creature gets -4/-2 until end of turn.

Pestilent Spirit

Menace, deathtouch
Instant and sorcery spells you control have deathtouch. (Any amount of damage they deal to a creature is enough to destroy it.)

Last Gasp

Target creature gets -3/-3 until end of turn.

Burnt Offering

As an additional cost to cast this spell, sacrifice a creature.
Add X mana in any combination of {B} and/or {R}, where X is the sacrificed creature's mana value.

Dakmor Salvage

This land enters tapped.
{T}: Add {B}.
Dredge 2 (If you would draw a card, you may mill two cards instead. If you do, return this card from your graveyard to your hand.)

Strangling Soot

Destroy target creature with toughness 3 or less.
Flashback {5}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Smoke Bomb

Flash
All creatures have shroud. (They can't be the targets of spells or abilities.)
At the beginning of your upkeep, sacrifice this artifact. When you do, target creature you control can't be blocked this turn.

Dark Ritual

Feebleness

Flash
Enchant creature
Enchanted creature gets -2/-1.

Neutralize the Guards

Creatures target opponent controls get -1/-1 until end of turn. Surveil 2. (Look at the top two cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)