You can't win the game and your opponents can't lose the game.
6 /
6
{B}
Appetite for Brains
Sorcery
Target opponent reveals their hand. You choose a card from it with mana value 4 or greater and exile that card.
{3}{B}{B}
Archfiend of Depravity
Creature - Demon
Flying
At the beginning of each opponent's end step, that player chooses up to two creatures they control, then sacrifices the rest.
5 /
4
--
Bojuka Bog
Land
Bojuka Bog enters the battlefield tapped.
When Bojuka Bog enters the battlefield, exile target player's graveyard.
{T}: Add {B}.
{3}
Bontu's Monument
Legendary Artifact
Black creature spells you cast cost {1} less to cast.
Whenever you cast a creature spell, each opponent loses 1 life and you gain 1 life.
{1}{B}
Cabal Ritual
Instant
Add {B}{B}{B}.
Threshold -- Add {B}{B}{B}{B}{B} instead if seven or more cards are in your graveyard.
{1}{B}
Cruel Edict
Sorcery
Target opponent sacrifices a creature.
{B}
Cry of Contrition
Sorcery
Target player discards a card.
Haunt (When this spell card is put into a graveyard after resolving, exile it haunting target creature.)
When the creature Cry of Contrition haunts dies, target player discards a card.
{B}
Dark Ritual
Instant
Add {B}{B}{B}.
{2}{B}
Davriel, Rogue Shadowmage
Legendary Planeswalker - Davriel
At the beginning of each opponent's upkeep, if that player has one or fewer cards in hand, Davriel, Rogue Shadowmage deals 2 damage to them.
-1: Target player discards a card.
L:
3
{X}{B}{B}
Death Denied
Instant - Arcane
Return X target creature cards from your graveyard to your hand.
{2}{B}
Demogorgon's Clutches
Sorcery
Target opponent discards two cards, mills two cards, and loses 2 life. (To mill a card, a player puts the top card of their library into their graveyard.)
{3}{B}{B}
Demon of Wailing Agonies
Creature - Demon
Flying
Lieutenant -- As long as you control your commander, Demon of Wailing Agonies gets +2/+2 and has "Whenever Demon of Wailing Agonies deals combat damage to a player, that player sacrifices a creature."
4 /
4
{2}
Demon's Horn
Artifact
Whenever a player casts a black spell, you may gain 1 life.
{1}{B}
Demonic Gifts
Instant
Until end of turn, target creature gets +2/+0 and gains "When this creature dies, return it to the battlefield under its owner's control."
{2}{B}
Demonic Taskmaster
Creature - Demon
Flying
At the beginning of your upkeep, sacrifice a creature other than Demonic Taskmaster.
4 /
3
{B}
Demonic Vigor
Enchantment - Aura
Enchant creature
Enchanted creature gets +1/+1.
When enchanted creature dies, return that card to its owner's hand.
{2}{B}{B}
Desecration Demon
Creature - Demon
Flying
At the beginning of each combat, any opponent may sacrifice a creature. If a player does, tap Desecration Demon and put a +1/+1 counter on it.
6 /
6
{2}{B}{B}
Diabolic Tutor
Sorcery
Search your library for a card, put that card into your hand, then shuffle.
{B}
Disentomb
Sorcery
Return target creature card from your graveyard to your hand.
{3}{B}{B}
Doom Whisperer
Creature - Nightmare Demon
Flying, trample
Pay 2 life: 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.)
6 /
6
{1}{B}
Dream Devourer
Creature - Demon Cleric
Each nonland card in your hand without foretell has foretell. Its foretell cost is equal to its mana cost reduced by {2}. (During your turn, you may pay {2} and exile it from your hand face down. Cast it on a later turn for its foretell cost.)
Whenever you foretell a card, Dream Devourer gets +2/+0 until end of turn.
0 /
3
{7}
Elbrus, the Binding Blade
Legendary Artifact - Equipment
Equipped creature gets +1/+0.
When equipped creature deals combat damage to a player, unattach Elbrus, the Binding Blade, then transform it.
Equip {1}
--
Withengar Unbound
Legendary Creature - Demon
Flying, intimidate, trample (A creature with intimidate can't be blocked except by artifact creatures and/or creatures that share a color with it.)
Whenever a player loses the game, put thirteen +1/+1 counters on Withengar Unbound.
--
Evolving Wilds
Land
{T}, Sacrifice Evolving Wilds: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
{B}{B}
Fear
Enchantment - Aura
Enchant creature (Target a creature as you cast this. This card enters the battlefield attached to that creature.)
Enchanted creature has fear. (It can't be blocked except by artifact creatures and/or black creatures.)
{B}
Feign Death
Instant
Until end of turn, target creature gains "When this creature dies, return it to the battlefield tapped under its owner's control with a +1/+1 counter on it."
{2}{B}
Grisly Transformation
Enchantment - Aura
Enchant creature
When Grisly Transformation enters the battlefield, draw a card.
Enchanted creature has intimidate. (It can't be blocked except by artifact creatures and/or creatures that share a color with it.)
{2}{B}
Gruesome Encore
Sorcery
Put target creature card from an opponent's graveyard onto the battlefield under your control. It gains haste. Exile it at the beginning of the next end step. If that creature would leave the battlefield, exile it instead of putting it anywhere else.
{B}
Harsh Scrutiny
Sorcery
Target opponent reveals their hand. You choose a creature card from it. That player discards that card. Scry 1.
{4}{B}{B}
Harvester of Souls
Creature - Demon
Deathtouch
Whenever another nontoken creature dies, you may draw a card.
5 /
5
{5}{B}{B}
Herald of Anguish
Creature - Demon
Improvise (Your artifacts can help cast this spell. Each artifact you tap after you're done activating mana abilities pays for {1}.)
Flying
At the beginning of your end step, each opponent discards a card.
{1}{B}, Sacrifice an artifact: Target creature gets -2/-2 until end of turn.
5 /
5
{1}{B}{B}
Herald of Torment
Enchantment Creature - Demon
Bestow {3}{B}{B} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
Flying
At the beginning of your upkeep, you lose 1 life.
Enchanted creature gets +3/+3 and has flying.
3 /
3
{1}{B}{B}
Hero's Downfall
Instant
Destroy target creature or planeswalker.
{B}{B}
Hymn to Tourach
Sorcery
Target player discards two cards at random.
{3}{B}{B}
Indulgent Tormentor
Creature - Demon
Flying
At the beginning of your upkeep, draw a card unless target opponent sacrifices a creature or pays 3 life.
5 /
3
{2}
Jet Medallion
Artifact
Black spells you cast cost {1} less to cast.
{3}{B}{B}
Liliana Vess
Legendary Planeswalker - Liliana
+1: Target player discards a card.
-2: Search your library for a card, then shuffle and put that card on top.
-8: Put all creature cards from all graveyards onto the battlefield under your control.
L:
5
{2}{B}{B}
Liliana of the Dark Realms
Legendary Planeswalker - Liliana
+1: Search your library for a Swamp card, reveal it, put it into your hand, then shuffle.
-3: Target creature gets +X/+X or -X/-X until end of turn, where X is the number of Swamps you control.
-6: You get an emblem with "Swamps you control have '{T}: Add {B}{B}{B}{B}.'"
L:
3
{1}{B}{B}
Liliana's Specter
Creature - Specter
Flying
When Liliana's Specter enters the battlefield, each opponent discards a card.
2 /
1
{2}{B}{B}
Liliana, Waker of the Dead
Legendary Planeswalker - Liliana
+1: Each player discards a card. Each opponent who can't loses 3 life.
-3: Target creature gets -X/-X until end of turn, where X is the number of cards in your graveyard.
-7: You get an emblem with "At the beginning of combat on your turn, put target creature card from a graveyard onto the battlefield under your control. It gains haste."
L:
4
{3}{B}
March of the Returned
Sorcery
Return up to two target creature cards from your graveyard to your hand.
{2}{B}
Mark of the Oni
Enchantment - Aura
Enchant creature
You control enchanted creature.
At the beginning of the end step, if you control no Demons, sacrifice Mark of the Oni.
{2}{B}
Mind Rot
Sorcery
Target player discards two cards.
{2}{B}{B}
Mindwrack Demon
Creature - Demon
Flying, trample
When Mindwrack Demon enters the battlefield, mill four cards.
Delirium -- At the beginning of your upkeep, you lose 4 life unless there are four or more card types among cards in your graveyard.
4 /
5
{4}{B}{B}
Nefarox, Overlord of Grixis
Legendary Creature - Demon
Flying
Exalted (Whenever a creature you control attacks alone, that creature gets +1/+1 until end of turn.)
Whenever Nefarox, Overlord of Grixis attacks alone, defending player sacrifices a creature.
5 /
5
{3}{B}
Nightsnare
Sorcery
Target opponent reveals their hand. You may choose a nonland card from it. If you do, that player discards that card. If you don't, that player discards two cards.
{4}{B}{B}
Ob Nixilis, Unshackled
Legendary Creature - Demon
Flying, trample
Whenever an opponent searches their library, that player sacrifices a creature and loses 10 life.
Whenever another creature dies, put a +1/+1 counter on Ob Nixilis, Unshackled.
4 /
4
{3}{B}{B}
Ob Nixilis, the Fallen
Legendary Creature - Demon
Landfall -- Whenever a land enters the battlefield under your control, you may have target player lose 3 life. If you do, put three +1/+1 counters on Ob Nixilis, the Fallen.
3 /
3
{1}{B}
Pit Keeper
Creature - Human Wizard
When Pit Keeper enters the battlefield, if you have four or more creature cards in your graveyard, you may return target creature card from your graveyard to your hand.
2 /
1
--
Radiant Fountain
Land
When Radiant Fountain enters the battlefield, you gain 2 life.
{T}: Add {C}.
{2}{B}
Rakdos Drake
Creature - Drake
Flying
Unleash (You may have this creature enter the battlefield with a +1/+1 counter on it. It can't block as long as it has a +1/+1 counter on it.)
1 /
2
{3}{B}{B}{B}
Reaper from the Abyss
Creature - Demon
Flying
Morbid -- At the beginning of each end step, if a creature died this turn, destroy target non-Demon creature.
6 /
6
{2}{B}
Recover
Sorcery
Return target creature card from your graveyard to your hand.
Draw a card.
{4}{B}{B}
Reign of the Pit
Sorcery
Each player sacrifices a creature. Create an X/X black Demon creature token with flying, where X is the total power of the creatures sacrificed this way.
{2}{B}{B}
Sangromancer
Creature - Vampire Shaman
Flying
Whenever a creature an opponent controls dies, you may gain 3 life.
Whenever an opponent discards a card, you may gain 3 life.
3 /
3
{5}{B}{B}
Sheoldred, Whispering One
Legendary Creature - Phyrexian Praetor
Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
At the beginning of your upkeep, return target creature card from your graveyard to the battlefield.
At the beginning of each opponent's upkeep, that player sacrifices a creature.
6 /
6
{B}{B}
Smallpox
Sorcery
Each player loses 1 life, discards a card, sacrifices a creature, then sacrifices a land.
{1}{B}{B}
Soulcage Fiend
Creature - Demon
When Soulcage Fiend dies, each player loses 3 life.
3 /
2
{3}
Staff of the Death Magus
Artifact
Whenever you cast a black spell or a Swamp enters the battlefield under your control, you gain 1 life.
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
--
Swamp
Basic Land - Swamp
({T}: Add {B}.)
{1}{B}{B}
Syphon Life
Sorcery
Target player loses 2 life and you gain 2 life.
Retrace (You may cast this card from your graveyard by discarding a land card in addition to paying its other costs.)
{3}{B}
Tendrils of Corruption
Instant
Tendrils of Corruption deals X damage to target creature and you gain X life, where X is the number of Swamps you control.
{3}{B}{B}
Tergrid, God of Fright
Legendary Creature - God
Menace
Whenever an opponent sacrifices a nontoken permanent or discards a permanent card, you may put that card from a graveyard onto the battlefield under your control.
4 /
5
--
Tergrid's Lantern
Legendary Artifact
{T}: Target player loses 3 life unless they sacrifice a nonland permanent or discard a card.
{3}{B}: Untap Tergrid's Lantern.
4 /
5
{3}{B}
Tree of Perdition
Creature - Plant
Defender
{T}: Exchange target opponent's life total with Tree of Perdition's toughness.
0 /
13
--
Tyrite Sanctum
Land
{T}: Add {C}.
{2}, {T}: Target legendary creature becomes a God in addition to its other types. Put a +1/+1 counter on it.
{4}, {T}, Sacrifice Tyrite Sanctum: Put an indestructible counter on target God.
--
Urborg, Tomb of Yawgmoth
Legendary Land
Each land is a Swamp in addition to its other land types.
{2}{B}
Varragoth, Bloodsky Sire
Legendary Creature - Demon Rogue
Deathtouch
Boast -- {1}{B}: Target player searches their library for a card, then shuffles and puts that card on top. (Activate only if this creature attacked this turn and only once each turn.)
2 /
3
{2}{B}
Victimize
Sorcery
Choose two target creature cards in your graveyard. Sacrifice a creature. If you do, return the chosen cards to the battlefield tapped.
{2}{B}
Waking Nightmare
Sorcery - Arcane
Target player discards two cards.
{5}{B}{B}
Wit's End
Sorcery
Target player discards their hand.
{B}{B}
Wrench Mind
Sorcery
Target player discards two cards unless they discard an artifact card.