You can't win the game and your opponents can't lose the game.
6 /
6
{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
{1}{B}
Blade of the Oni
Artifact Creature - Equipment Demon
Menace
Equipped creature has base power and toughness 5/5, has menace, and is a black Demon in addition to its other colors and types.
Reconfigure {2}{B}{B} ({2}{B}{B}: Attach to target creature you control; or unattach from a creature. Reconfigure only as a sorcery. While attached, this isn't a creature.)
3 /
1
--
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.
--
Castle Locthwain
Land
Castle Locthwain enters the battlefield tapped unless you control a Swamp.
{T}: Add {B}.
{1}{B}{B}, {T}: Draw a card, then you lose life equal to the number of cards in your hand.
--
Cathedral of War
Land
Cathedral of War enters the battlefield tapped.
Exalted (Whenever a creature you control attacks alone, that creature gets +1/+1 until end of turn.)
{T}: Add {C}.
--
Command Beacon
Land
{T}: Add {C}.
{T}, Sacrifice Command Beacon: Put your commander into your hand from the command zone.
{3}
Crystal Ball
Artifact
{1}, {T}: Scry 2. (Look at the top two cards of your library, then put any number of them on the bottom of your library and the rest on top in any order.)
{2}{B}{B}
Damnation
Sorcery
Destroy all creatures. They can't be regenerated.
{B}
Dark Ritual
Instant
Add {B}{B}{B}.
{X}{B}{B}
Death Denied
Instant - Arcane
Return X target creature cards from your graveyard to your hand.
{5}{B}{B}
Demon of Loathing
Creature - Demon
Flying, trample
Whenever Demon of Loathing deals combat damage to a player, that player sacrifices a creature.
7 /
7
{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."
{1}{B}
Demonic Tutor
Sorcery
Search your library for a card, put that card into your hand, then shuffle.
{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.
{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
{4}
Door of Destinies
Artifact
As Door of Destinies enters the battlefield, choose a creature type.
Whenever you cast a spell of the chosen type, put a charge counter on Door of Destinies.
Creatures you control of the chosen type get +1/+1 for each charge counter on Door of Destinies.
{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.
{1}{B}{B}
Embodiment of Agonies
Creature - Demon
Flying, deathtouch
Embodiment of Agonies enters the battlefield 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.)
0 /
0
{X}{X}{B}{B}{B}
Entreat the Dead
Sorcery
Return X target creature cards from your graveyard to the battlefield.
Miracle {X}{B}{B} (You may cast this card for its miracle cost when you draw it if it's the first card you drew this turn.)
{X}{B}{B}
Exsanguinate
Sorcery
Each opponent loses X life. You gain life equal to the life lost this way.
{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."
{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
{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.
{1}{B}
Leech Gauntlet
Artifact Creature - Equipment Leech
Lifelink
Equipped creature has lifelink.
Reconfigure {4} ({4}: Attach to target creature you control; or unattach from a creature. Reconfigure only as a sorcery. While attached, this isn't a creature.)
2 /
2
{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
{3}{B}{B}
Liliana's Contract
Enchantment
When Liliana's Contract enters the battlefield, you draw four cards and you lose 4 life.
At the beginning of your upkeep, if you control four or more Demons with different names, you win the game.
{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
{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}{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
--
Mirrorpool
Land
Mirrorpool enters the battlefield tapped.
{T}: Add {C}.
{2}{C}, {T}, Sacrifice Mirrorpool: Copy target instant or sorcery spell you control. You may choose new targets for the copy.
{4}{C}, {T}, Sacrifice Mirrorpool: Create a token that's a copy of target creature you control.
{4}
Nyx Lotus
Legendary Artifact
Nyx Lotus enters the battlefield tapped.
{T}: Choose a color. Add an amount of mana of that color equal to your devotion to that color. (Your devotion to a color is the number of mana symbols of that color in the mana costs of permanents you control.)
{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}{B}
Phyrexian Arena
Enchantment
At the beginning of your upkeep, you draw a card and you lose 1 life.
{3}{B}
Plague Drone
Creature - Demon
Flying
Rot Fly -- If an opponent would gain life, that player loses that much life instead.
3 /
3
--
Radiant Fountain
Land
When Radiant Fountain enters the battlefield, you gain 2 life.
{T}: Add {C}.
{B}
Reanimate
Sorcery
Put target creature card from a graveyard onto the battlefield under your control. You lose life equal to its mana value.
{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
{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.
{4}{B}{B}{B}{B}
Reiver Demon
Creature - Demon
Flying
When Reiver Demon enters the battlefield, if you cast it from your hand, destroy all nonartifact, nonblack creatures. They can't be regenerated.
6 /
6
{1}{B}
Rune of Mortality
Enchantment - Aura Rune
Enchant permanent
When Rune of Mortality enters the battlefield, draw a card.
As long as enchanted permanent is a creature, it has deathtouch.
As long as enchanted permanent is an Equipment, it has "Equipped creature has deathtouch."
{5}{B}{B}
Rune-Scarred Demon
Creature - Demon
Flying
When Rune-Scarred Demon enters the battlefield, search your library for a card, put it into your hand, then shuffle.
6 /
6
{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
--
Snow-Covered Swamp
Basic Snow Land - Swamp
({T}: Add {B}.)
{1}
Sol Ring
Artifact
{T}: Add {C}{C}.
{1}{B}{B}
Soulcage Fiend
Creature - Demon
When Soulcage Fiend dies, each player loses 3 life.
3 /
2
{4}{B}{B}
Sower of Discord
Creature - Demon
Flying
As Sower of Discord enters the battlefield, choose two players.
Whenever damage is dealt to one of the chosen players, the other chosen player also loses that much life.
6 /
6
{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}.)
{2}
Swiftfoot Boots
Artifact - Equipment
Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control.)
Equip {1}
{3}{B}
Syphon Mind
Sorcery
Each other player discards a card. You draw a card for each card discarded this way.
{2}{B}
Taborax, Hope's Demise
Legendary Creature - Demon Cleric
Flying
Taborax, Hope's Demise has lifelink as long as it has five or more +1/+1 counters on it.
Whenever another nontoken creature you control dies, put a +1/+1 counter on Taborax. If that creature was a Cleric, you may draw a card. If you do, you lose 1 life.
2 /
2
{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
{X}{B}{B}
The Meathook Massacre
Legendary Enchantment
When The Meathook Massacre enters the battlefield, each creature gets -X/-X until end of turn.
Whenever a creature you control dies, each opponent loses 1 life.
Whenever a creature an opponent controls dies, you gain 1 life.
{X}{B}{B}
Torment of Hailfire
Sorcery
Repeat the following process X times. Each opponent loses 3 life unless that player sacrifices a nonland permanent or discards a card.
{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.
{B}{B}{B}
Underworld Dreams
Enchantment
Whenever an opponent draws a card, Underworld Dreams deals 1 damage to that player.
--
Urborg, Tomb of Yawgmoth
Legendary Land
Each land is a Swamp in addition to its other land types.
{5}
Vanquisher's Banner
Artifact
As Vanquisher's Banner enters the battlefield, choose a creature type.
Creatures you control of the chosen type get +1/+1.
Whenever you cast a creature spell of the chosen type, draw a card.
{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
{3}{B}
Venomcrawler
Artifact Creature - Demon
Lifelink
Devourer of Souls -- Whenever another creature dies, put a +1/+1 counter on Venomcrawler.
2 /
2
{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.
{5}{B}{B}{B}
Vilis, Broker of Blood
Legendary Creature - Demon
Flying
{B}, Pay 2 life: Target creature gets -1/-1 until end of turn.
Whenever you lose life, draw that many cards. (Damage causes loss of life.)