Have

Chaos Mutation

Exile any number of target creatures controlled by different players. For each creature exiled this way, its controller reveals cards from the top of their library until they reveal a creature card, puts that card onto the battlefield, then puts the rest on the bottom of their library in a random order.

Soulbringer Approves

Demon of Dark Schemes

Flying
When this creature enters, all other creatures get -2/-2 until end of turn.
Whenever another creature dies, you get {E} (an energy counter).
{2}{B}, Pay {E}{E}{E}{E}: Put target creature card from a graveyard onto the battlefield under your control tapped.

Let the Galaxy Burn

Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)
Let the Galaxy Burn deals X plus 2 damage to each creature that didn't enter this turn.

Chaos Terminator Lord

Lord of Chaos — At the beginning of combat on your turn, another target creature you control gains double strike until end of turn.

Dimir Locket

{T}: Add {U} or {B}.
{U/B}{U/B}{U/B}{U/B}, {T}, Sacrifice this artifact: Draw two cards.

Maybe?

Skirsdag High Priest

Morbid — {T}, Tap two untapped creatures you control: Create a 5/5 black Demon creature token with flying. Activate only if a creature died this turn.

Be'lakor, the Dark Master

Flying
Prince of Chaos — When Be'lakor enters, you draw X cards and you lose X life, where X is the number of Demons you control.
Lord of Torment — Whenever another Demon you control enters, it deals damage equal to its power to any target.

Soulbringer Disapproves

Swiftwater Cliffs

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

Seeker of Slaanesh

Haste
Allure of Slaanesh — Each opponent must attack with at least one creature each combat if able.

Abaddon the Despoiler

Trample
Mark of Chaos Ascendant — During your turn, spells you cast from your hand with mana value X or less have cascade, where X is the total amount of life your opponents have lost this turn.

Embodiment of Agonies

Flying, deathtouch
This creature enters with a +1/+1 counter on it for each different mana cost among nonland cards in your graveyard. (For example, {2}{B} and {1}{B}{B} are different mana costs.)

Bedevil

Destroy target artifact, creature, or planeswalker.

Forgotten Cave

This land enters tapped.
{T}: Add {R}.
Cycling {R} ({R}, Discard this card: Draw a card.)

Poxwalkers

Deathtouch
Curse of the Walking Pox — Whenever you cast a spell from anywhere other than your hand, return this card from your graveyard to the battlefield tapped.

Demonic Rising

At the beginning of your end step, if you control exactly one creature, create a 5/5 black Demon creature token with flying.

Pink Horror

Coruscating Flames — Whenever you cast an instant or sorcery spell, this creature deals 2 damage to any target.
Split — When this creature dies, create two 2/2 blue and red Demon Horror creature tokens named Blue Horror with "Whenever you cast an instant or sorcery spell, this token deals 1 damage to any target."

Rakdos Cluestone

{T}: Add {B} or {R}.
{B}{R}, {T}, Sacrifice this artifact: Draw a card.

Bile Blight

Target creature and all other creatures with the same name as that creature get -3/-3 until end of turn.

Temple of Malice

This land enters tapped.
When this land enters, scry 1. (Look at the top card of your library. You may put that card on the bottom.)
{T}: Add {B} or {R}.

Bloodcrusher of Khorne

Trample
Devastating Charge — Other creatures you control have trample.

Lord of Change

Flying, ward {3}
Architect of Deception — When this creature enters, draw three cards.

Dimir Cluestone

{T}: Add {U} or {B}.
{U}{B}, {T}, Sacrifice this artifact: Draw a card.

Molten Slagheap

{T}: Add {C}.
{1}, {T}: Put a storage counter on this land.
{1}, Remove X storage counters from this land: Add X mana in any combination of {B} and/or {R}.

Séance Board

Morbid — At the beginning of each end step, if a creature died this turn, put a soul counter on this artifact.
{T}: Add X mana of any one color, where X is the number of soul counters on this artifact. Spend this mana only to cast instant, sorcery, Demon, and Spirit spells.

Temple of the False God

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

Khârn the Betrayer

Berzerker — Khârn the Betrayer attacks or blocks each combat if able.
Sigil of Corruption — When you lose control of Khârn the Betrayer, draw two cards.
The Betrayer — If damage would be dealt to Khârn the Betrayer, prevent that damage and an opponent of your choice gains control of it.

Reign of the Pit

Each player sacrifices a creature of their choice. Create an X/X black Demon creature token with flying, where X is the total power of the creatures sacrificed this way.

Evolving Wilds

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

Mortarion, Daemon Primarch

Flying
Primarch of the Death Guard — At the beginning of your end step, you may pay {X}. If you do, create X 2/2 black Astartes Warrior creature tokens with menace. X can't be greater than the amount of life you lost this turn.

Mandate of Abaddon

Choose target creature you control. Destroy all creatures with power less than that creature's power.

Brainstorm

Draw three cards, then put two cards from your hand on top of your library in any order.

Smoldering Marsh

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

Venomcrawler

Lifelink
Devourer of Souls — Whenever another creature dies, put a +1/+1 counter on this creature.

Blood for the Blood God!

This spell costs {1} less to cast for each creature that died this turn.
Discard your hand, then draw eight cards. Blood for the Blood God! deals 8 damage to each opponent. Exile Blood for the Blood God!

Inquisitor Eisenhorn

You may reveal the first card you draw each turn as you draw it. Whenever you reveal an instant or sorcery card this way, create Cherubael, a legendary 4/4 black Demon creature token with flying.
Whenever Inquisitor Eisenhorn deals combat damage to a player, investigate that many times. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")

Lucius the Eternal

Haste
Armour of Shrieking Souls — When Lucius the Eternal dies, exile it and choose target creature an opponent controls. When that creature leaves the battlefield, return this card from exile to the battlefield under its owner's control.

Worn Powerstone

This artifact enters tapped.
{T}: Add {C}{C}.

Crumbling Necropolis

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

Talisman of Creativity

{T}: Add {C}.
{T}: Add {U} or {R}. This artifact deals 1 damage to you.

Dark Apostle

Gift of Chaos — {3}, {T}: The next noncreature spell you cast this turn has cascade. (When you cast that spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)

Magnus the Red

Flying
Unearthly Power — Instant and sorcery spells you cast cost {1} less to cast for each creature token you control.
Blade of Magnus — Whenever Magnus the Red deals combat damage to a player, create a 3/3 red Spawn creature token.

Ob Nixilis of the Black Oath

+2: Each opponent loses 1 life. You gain life equal to the life lost this way.
−2: Create a 5/5 black Demon creature token with flying. You lose 2 life.
−8: You get an emblem with "{1}{B}, Sacrifice a creature: You gain X life and draw X cards, where X is the sacrificed creature's power."
Ob Nixilis of the Black Oath can be your commander.

Deny Reality

Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)
Return target permanent to its owner's hand.

Dreadfeast Demon

Flying
At the beginning of your end step, sacrifice a non-Demon creature. If you do, create a token that's a copy of this creature.

Drach'Nyen

Echo of the First Murder — When Drach'Nyen enters, exile up to one target creature.
Daemon Sword — Equipped creature has menace and gets +X/+0, where X is the exiled card's power.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Rakdos, Patron of Chaos

Flying, trample
At the beginning of your end step, target opponent may sacrifice two nonland, nontoken permanents of their choice. If they don't, you draw two cards.

Kill! Maim! Burn!

Choose one or more —
• Destroy target artifact.
• Destroy target creature.
• Kill! Maim! Burn! deals 3 damage to target player.

Past in Flames

Each instant and sorcery card in your graveyard gains flashback until end of turn. The flashback cost is equal to its mana cost.
Flashback {4}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Blight Grenade

Destroy target creature.
All creatures get -3/-3 until end of turn.

Prince of Thralls

Whenever a permanent an opponent controls is put into a graveyard, put that card onto the battlefield under your control unless that opponent pays 3 life.

Wayfarer's Bauble

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

Bituminous Blast

Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)
Bituminous Blast deals 4 damage to target creature.

Exalted Flamer of Tzeentch

Sorcerous Inspiration — At the beginning of your upkeep, return an instant or sorcery card at random from your graveyard to your hand.
Fire of Tzeentch — Whenever you cast an instant or sorcery spell, this creature deals 1 damage to each opponent.

Sol Ring

Terramorphic Expanse

Reaper from the Abyss

Flying
Morbid — At the beginning of each end step, if a creature died this turn, destroy target non-Demon creature.

Chromatic Lantern

Lands you control have "{T}: Add one mana of any color."
{T}: Add one mana of any color.

Thriving Moor

This land enters tapped. As it enters, choose a color other than black.
{T}: Add {B} or one mana of the chosen color.

Path of Ancestry

This land enters tapped.
{T}: Add one mana of any color in your commander's color identity. When that mana is spent to cast a creature spell that shares a creature type with your commander, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Assault Suit

Equipped creature gets +2/+2, has haste, can't attack you or planeswalkers you control, and can't be sacrificed.
At the beginning of each opponent's upkeep, you may have that player gain control of equipped creature until end of turn. If you do, untap it.
Equip {3}

Swamp

Exotic Orchard

{T}: Add one mana of any color that a land an opponent controls could produce.

Rakdos Locket

{T}: Add {B} or {R}.
{B/R}{B/R}{B/R}{B/R}, {T}, Sacrifice this artifact: Draw two cards.

Barren Moor

This land enters tapped.
{T}: Add {B}.
Cycling {B} ({B}, Discard this card: Draw a card.)

The Lost and the Damned

Whenever a land you control enters from anywhere other than your hand or you cast a spell from anywhere other than your hand, create a 3/3 red Spawn creature token.

Tallyman of Nurgle

Lifelink
The Seven-fold Chant — At the beginning of your end step, if a creature died this turn, you draw a card and you lose 1 life. If seven or more creatures died this turn, instead you draw seven cards and you lose 7 life.

Warstorm Surge

Whenever a creature you control enters, it deals damage equal to its power to any target.

The Horus Heresy

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — For each opponent, gain control of up to one target nonlegendary creature that player controls for as long as this Saga remains on the battlefield.
II — Draw a card for each creature you control but don't own.
III — Starting with you, each player chooses a creature. Destroy each creature chosen this way.

Ritual Chamber

When you unlock this door, create a 6/6 black Demon creature token with flying.
(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)

Unholy Annex

At the beginning of your end step, draw a card. If you control a Demon, each opponent loses 2 life and you gain 2 life. Otherwise, you lose 2 life.
(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)

Unholy Annex // Ritual Chamber

Izzet Locket

{T}: Add {U} or {R}.
{U/R}{U/R}{U/R}{U/R}, {T}, Sacrifice this artifact: Draw two cards.

Sloppity Bilepiper

Jolly Gutpipes — {2}, {T}, Sacrifice a creature: The next creature spell you cast this turn has cascade. (When you next cast a creature spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)

Talisman of Indulgence

{T}: Add {C}.
{T}: Add {B} or {R}. This artifact deals 1 damage to you.

Temple of Deceit

This land enters tapped.
When this land enters, scry 1. (Look at the top card of your library. You may put that card on the bottom.)
{T}: Add {U} or {B}.

Foreboding Ruins

As this land enters, you may reveal a Swamp or Mountain card from your hand. If you don't, this land enters tapped.
{T}: Add {B} or {R}.

Command Tower

Helbrute

Haste
Sarcophagus — You may cast this card from your graveyard by exiling another creature card from your graveyard in addition to paying its other costs.

Chaos Defiler

Trample
Battle Cannon — When this creature enters or dies, for each opponent, choose a nonland permanent that player controls. Destroy one of them chosen at random.

Tzaangor Shaman

Flying
Sorcerous Elixir — Whenever this creature deals combat damage to a player, copy the next instant or sorcery spell you cast this turn when you cast it. You may choose new targets for the copy.

Dread Cacodemon

When this creature enters, if you cast it from your hand, destroy all creatures your opponents control, then tap all other creatures you control.

Tainted Peak

{T}: Add {C}.
{T}: Add {B} or {R}. Activate only if you control a Swamp.

Plague Drone

Flying
Rot Fly — If an opponent would gain life, that player loses that much life instead.

Rakdos, Lord of Riots

You can't cast Rakdos unless an opponent lost life this turn.
Flying, trample
Creature spells you cast cost {1} less to cast for each 1 life your opponents have lost this turn.

The Balrog of Moria

Trample, haste
When The Balrog of Moria dies, you may exile it. When you do, for each opponent, exile up to one target creature that player controls.
Cycling {3}{R} ({3}{R}, Discard this card: Draw a card.)
When you cycle this card, create two Treasure tokens.

Blasphemous Act

This spell costs {1} less to cast for each creature on the battlefield.
Blasphemous Act deals 13 damage to each creature.

Archfiend of Depravity

Flying
At the beginning of each opponent's end step, that player chooses up to two creatures they control, then sacrifices the rest.

Hedron Archive

{T}: Add {C}{C}.
{2}, {T}, Sacrifice this artifact: Draw two cards.

Raphael, Fiendish Savior

Flying
Other Demons, Devils, Imps, and Tieflings you control get +1/+1 and have lifelink.
At the beginning of each end step, if a creature card was put into your graveyard from anywhere this turn, create a 1/1 red Devil creature token with "When this token dies, it deals 1 damage to any target."

Demon of Wailing Agonies

Flying
Lieutenant — As long as you control your commander, this creature gets +2/+2 and has "Whenever this creature deals combat damage to a player, that player sacrifices a creature of their choice."

Commander's Sphere

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

Keeper of Secrets

First strike, haste
Symphony of Pain — Whenever you cast a spell from anywhere other than your hand, this creature deals damage equal to that spell's mana value to target opponent.

Heralds of Tzeentch

Flying
Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)

Dismal Backwater

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

Nurgle's Rot

Enchant creature an opponent controls
When enchanted creature dies, return this card to its owner's hand and you create a 1/3 black Demon creature token named Plaguebearer of Nurgle.

Mutalith Vortex Beast

Trample
Warp Vortex — When this creature enters, flip a coin for each opponent you have. For each flip you win, draw a card. For each flip you lose, this creature deals 3 damage to that player.

Dark Ritual

Knight Rampager

Trample
Frenzied Rampage — At the beginning of combat on your turn, choose an opponent at random. This creature attacks that player this combat if able.
When this creature dies, it deals 4 damage to target opponent chosen at random.

Herald of Slaanesh

Locus of Slaanesh — Demon spells you cast cost {2} less to cast.
Other Demons you control have haste.

Patchwork Banner

As this artifact enters, choose a creature type.
Creatures you control of the chosen type get +1/+1.
{T}: Add one mana of any color.

Withering Torment

Destroy target creature or enchantment. You lose 2 life.