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.

Command Beacon

{T}: Add {C}.
{T}, Sacrifice Command Beacon: Put your commander into your hand from the command zone.

Bojuka Bog

Bojuka Bog enters tapped.
When Bojuka Bog enters, exile target player's graveyard.
{T}: Add {B}.

Immersturm Skullcairn

Immersturm Skullcairn enters tapped.
{T}: Add {B}.
{1}{B}{R}{R}, {T}, Sacrifice Immersturm Skullcairn: It deals 3 damage to target player. That player discards a card. Activate only as a sorcery.

Viscera Seer

Sacrifice a creature: Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Flayer of the Hatebound

Undying (When this creature dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)
Whenever Flayer of the Hatebound or another creature enters from your graveyard, that creature deals damage equal to its power to any target.

Faithless Looting

Draw two cards, then discard two cards.
Flashback {2}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Chain Devil

Animate Chains — When Chain Devil enters, each player sacrifices a nontoken creature of their choice.

Zurzoth, Chaos Rider

Whenever an opponent draws their first card each turn, if it's not their turn, you create a 1/1 red Devil creature token with "When this creature dies, it deals 1 damage to any target."
Whenever one or more Devils you control attack one or more players, you and those players each draw a card, then discard a card at random.

Deathgreeter

Whenever another creature dies, you may gain 1 life.

Blackcleave Cliffs

Blackcleave Cliffs enters tapped unless you control two or fewer other lands.
{T}: Add {B} or {R}.

Blood Artist

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

Mahadi, Emporium Master

At the beginning of your end step, create a Treasure token for each creature that died this turn. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Vexing Devil

When Vexing Devil enters, any opponent may have it deal 4 damage to them. If a player does, sacrifice Vexing Devil.

Bedevil

Destroy target artifact, creature, or planeswalker.

Dragonskull Summit

Dragonskull Summit enters tapped unless you control a Swamp or a Mountain.
{T}: Add {B} or {R}.

Doomed Dissenter

When Doomed Dissenter dies, create a 2/2 black Zombie creature token.

Sin Prodder

Menace
At the beginning of your upkeep, reveal the top card of your library. Any opponent may have you put that card into your graveyard. If a player does, Sin Prodder deals damage to that player equal to that card's mana value. Otherwise, put that card into your hand.

Terminate

Destroy target creature. It can't be regenerated.

Phyrexian Arena

At the beginning of your upkeep, you draw a card and you lose 1 life.

Haunted Ridge

Haunted Ridge enters tapped unless you control two or more other lands.
{T}: Add {B} or {R}.

Sulfurous Springs

{T}: Add {C}.
{T}: Add {B} or {R}. Sulfurous Springs deals 1 damage to you.

Command Tower

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

Rakdos Charm

Choose one —
• Exile target player's graveyard.
• Destroy target artifact.
• Each creature deals 1 damage to its controller.

Plaguecrafter

When Plaguecrafter enters, each player sacrifices a creature or planeswalker of their choice. Each player who can't discards a card.

Ob Nixilis, the Adversary

Casualty X. The copy isn't legendary and has starting loyalty X. (As you cast this spell, you may sacrifice a creature with power X. When you do, copy this spell. The copy becomes a token.)
+1: Each opponent loses 2 life unless they discard a card. If you control a Demon or Devil, you gain 2 life.
−2: Create a 1/1 red Devil creature token with "When this creature dies, it deals 1 damage to any target."
−7: Target player draws seven cards and loses 7 life.

Spiteful Prankster

During your turn, Spiteful Prankster has first strike.
Whenever another creature dies, Spiteful Prankster deals 1 damage to target player or planeswalker.

Demonic Tutor

Search your library for a card, put that card into your hand, then shuffle.

Judith, the Scourge Diva

Other creatures you control get +1/+0.
Whenever a nontoken creature you control dies, Judith, the Scourge Diva deals 1 damage to any target.

Necrosynthesis

Enchant creature
Enchanted creature has "Whenever another creature dies, put a +1/+1 counter on this creature."
When enchanted creature dies, look at the top X cards of your library, where X is its power. Put one of those cards into your hand and the rest on the bottom of your library in a random order.

Juri, Master of the Revue

Whenever you sacrifice a permanent, put a +1/+1 counter on Juri, Master of the Revue.
When Juri dies, it deals damage equal to its power to any target.

Dig Up the Body

Casualty 1 (As you cast this spell, you may sacrifice a creature with power 1 or greater. When you do, copy this spell.)
Mill two cards, then you may return a creature card from your graveyard to your hand. (To mill a card, put the top card of your library into your graveyard.)

Swamp

Falkenrath Noble

Flying
Whenever Falkenrath Noble or another creature dies, target player loses 1 life and you gain 1 life.

Dreadbore

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.

Rakdos Cackler

Unleash (You may have this creature enter with a +1/+1 counter on it. It can't block as long as it has a +1/+1 counter on it.)

Hobblefiend

Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)
{1}, Sacrifice another creature: Put a +1/+1 counter on Hobblefiend.

Rob the Archives

Casualty 1 (As you cast this spell, you may sacrifice a creature with power 1 or greater. When you do, copy this spell.)
Exile the top two cards of your library. You may play those cards this turn.

Mayhem Devil

Whenever a player sacrifices a permanent, Mayhem Devil deals 1 damage to any target.

Footlight Fiend

When Footlight Fiend dies, it deals 1 damage to any target.

Blood Crypt

({T}: Add {B} or {R}.)
As Blood Crypt enters, you may pay 2 life. If you don't, it enters tapped.

Mountain

Vengeful Devil

Haste
Morbid — {T}: Vengeful Devil deals 1 damage to any target. Activate only if a creature died this turn.

Grave Pact

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

Hellrider

Haste
Whenever a creature you control attacks, Hellrider deals 1 damage to the player or planeswalker it's attacking.

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 creature dies, it deals 1 damage to any target."