Ob Nixilis, Unshackled

Flying, trample
Whenever an opponent searches their library, that player sacrifices a creature of their choice and loses 10 life.
Whenever another creature dies, put a +1/+1 counter on Ob Nixilis, Unshackled.

Ormendahl, the Corrupter

Flying, trample, lifelink
Sacrifice another creature: Draw a card.

Jerren, Corrupted Bishop

Whenever Jerren, Corrupted Bishop enters or another nontoken Human you control dies, you lose 1 life and create a 1/1 white Human creature token.
{2}: Target Human you control gains lifelink until end of turn.
At the beginning of your end step, if you have exactly 13 life, you may pay {4}{B}{B}. If you do, transform Jerren.

Jerren, Corrupted Bishop // Ormendahl, the Corrupter

Go for the Throat

Dark Ritual

Sol Ring

Cabal Stronghold

{T}: Add {C}.
{3}, {T}: Add {B} for each basic Swamp you control.

Ormendahl, Profane Prince

Westvale Abbey

{T}: Add {C}.
{5}, {T}, Pay 1 life: Create a 1/1 white and black Human Cleric creature token.
{5}, {T}, Sacrifice five creatures: Transform Westvale Abbey, then untap it.

Westvale Abbey // Ormendahl, Profane Prince

Cut Down

Destroy target creature with total power and toughness 5 or less.

Sanguinary Priest

Lifelink
Blood Chalice — Whenever another creature you control dies, Sanguinary Priest deals 1 damage to any target.

Liliana of the Dark Realms

+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}.'"

Cabal Coffers

{2}, {T}: Add {B} for each Swamp you control.

Songs of the Damned

Add {B} for each creature card in your graveyard.

Phyrexian Reclamation

{1}{B}, Pay 2 life: Return target creature card from your graveyard to your hand.

Blood Pact

Target player draws two cards and loses 2 life.

Patriarch's Bidding

Each player chooses a creature type. Each player returns all creature cards of a type chosen this way from their graveyard to the battlefield.

Bone Shards

As an additional cost to cast this spell, sacrifice a creature or discard a card.
Destroy target creature or planeswalker.

Defile

Target creature gets -1/-1 until end of turn for each Swamp you control.

Swamp

Urborg, Tomb of Yawgmoth

Each land is a Swamp in addition to its other land types.

Whisper, Blood Liturgist

{T}, Sacrifice two creatures: Return target creature card from your graveyard to the battlefield.

Thought Vessel

You have no maximum hand size.
{T}: Add {C}.

Echoing Return

Return target creature card and all other cards with the same name as that card from your graveyard to your hand.

Crypt Ghast

Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)
Whenever you tap a Swamp for mana, add an additional {B}.

Master of Dark Rites

{T}, Sacrifice another creature: Add {B}{B}{B}. Spend this mana only to cast Vampire, Cleric, and/or Demon spells.

Infernal Grasp

Destroy target creature. You lose 2 life.

Village Rites

As an additional cost to cast this spell, sacrifice a creature.
Draw two cards.

Victimize

Choose two target creature cards in your graveyard. Sacrifice a creature. If you do, return the chosen cards to the battlefield tapped.

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.

Kindred Dominance

Choose a creature type. Destroy all creatures that aren't of the chosen type.

Grave Pact

Whenever a creature you control dies, each other player sacrifices a creature of their choice.

No Rest for the Wicked

Sacrifice No Rest for the Wicked: Return to your hand all creature cards in your graveyard that were put there from the battlefield this turn.

Great Unclean One

Reverberating Summons — At the beginning of your end step, each opponent loses 2 life. Then for each opponent who has less life than you, create a 1/3 black Demon creature token named Plaguebearer of Nurgle.

Vilis, Broker of Blood

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.)

Secret Salvage

Exile target nonland card from your graveyard. Search your library for any number of cards with the same name as that card, reveal them, put them into your hand, then shuffle.

Razaketh, the Foulblooded

Flying, trample
Pay 2 life, Sacrifice another creature: Search your library for a card, put that card into your hand, then shuffle.

Thrumming Stone

Spells you cast have ripple 4. (Whenever you cast a spell, you may reveal the top four cards of your library. You may cast spells with the same name as that spell from among the revealed cards without paying their mana costs. Put the rest on the bottom of your library.)

Priest of Forgotten Gods

{T}, Sacrifice two other creatures: Any number of target players each lose 2 life and sacrifice a creature of their choice. You add {B}{B} and draw a card.

Shadow-Rite Priest

Other Clerics you control get +1/+1.
{3}{B}{B}, {T}, Sacrifice another Cleric: Search your library for a black creature card, put it onto the battlefield, then shuffle.

Varragoth, Bloodsky Sire

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.)

Black Market

Whenever a creature dies, put a charge counter on Black Market.
At the beginning of your first main phase, add {B} for each charge counter on Black Market.

Ancient Craving

You draw three cards and you lose 3 life.

Blood Artist

Whenever Blood Artist or another creature dies, target player loses 1 life and you gain 1 life.

Archfiend's Vessel

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
When Archfiend's Vessel enters, if it entered from your graveyard or you cast it from your graveyard, exile it. If you do, create a 5/5 black Demon creature token with flying.

Arcane Signet

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

Doomed Necromancer

{B}, {T}, Sacrifice Doomed Necromancer: Return target creature card from your graveyard to the battlefield.

Gray Merchant of Asphodel

When Gray Merchant of Asphodel enters, each opponent loses X life, where X is your devotion to black. You gain life equal to the life lost this way. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)

Liliana's Contract

When Liliana's Contract enters, 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.

Harvester of Souls

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)
Whenever another nontoken creature dies, you may draw a card.

Shadowborn Apostle

A deck can have any number of cards named Shadowborn Apostle.
{B}, Sacrifice six creatures named Shadowborn Apostle: Search your library for a Demon creature card, put it onto the battlefield, then shuffle.

Taborax, Hope's Demise

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.