Chain Reaction

Chain Reaction deals X damage to each creature, where X is the number of creatures on the battlefield.

Underworld Dreams

Whenever an opponent draws a card, Underworld Dreams deals 1 damage to that player.

Mogis, God of Slaughter

Indestructible
As long as your devotion to black and red is less than seven, Mogis isn't a creature.
At the beginning of each opponent's upkeep, Mogis deals 2 damage to that player unless they sacrifice a creature of their choice.

Rakdos Signet

Sulfuric Vortex

At the beginning of each player's upkeep, Sulfuric Vortex deals 2 damage to that player.
If a player would gain life, that player gains no life instead.

Bedevil

Destroy target artifact, creature, or planeswalker.

Black Sun's Zenith

Put X -1/-1 counters on each creature. Shuffle Black Sun's Zenith into its owner's library.

Braid of Fire

Cumulative upkeep—Add {R}. (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)

Drossforge Bridge

Drossforge Bridge enters tapped.
Indestructible
{T}: Add {B} or {R}.

Prismatic Lens

{T}: Add {C}.
{1}, {T}: Add one mana of any color.

Bloodchief Ascension

At the beginning of each end step, if an opponent lost 2 or more life this turn, you may put a quest counter on Bloodchief Ascension. (Damage causes loss of life.)
Whenever a card is put into an opponent's graveyard from anywhere, if Bloodchief Ascension has three or more quest counters on it, you may have that player lose 2 life. If you do, you gain 2 life.

Swamp

Foreboding Ruins

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

Mastermind's Acquisition

Choose one —
• Search your library for a card, put it into your hand, then shuffle.
• Put a card you own from outside the game into your hand.

Glacial Chasm

Cumulative upkeep—Pay 2 life. (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
When Glacial Chasm enters, sacrifice a land.
Creatures you control can't attack.
Prevent all damage that would be dealt to you.

Command Tower

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

Stuffy Doll

Indestructible
As Stuffy Doll enters, choose a player.
Whenever Stuffy Doll is dealt damage, it deals that much damage to the chosen player.
{T}: Stuffy Doll deals 1 damage to itself.

Vessel of Volatility

{1}{R}, Sacrifice Vessel of Volatility: Add {R}{R}{R}{R}.

Terminate

Destroy target creature. It can't be regenerated.

Talisman of Indulgence

{T}: Add {C}.
{T}: Add {B} or {R}. Talisman of Indulgence deals 1 damage to you.

Worldfire

Exile all permanents. Exile all cards from all hands and graveyards. Each player's life total becomes 1.

Fellwar Stone

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

Havoc Festival

Players can't gain life.
At the beginning of each player's upkeep, that player loses half their life, rounded up.

Obliterate

This spell can't be countered.
Destroy all artifacts, creatures, and lands. They can't be regenerated.

Seething Song

Peer into the Abyss

Target player draws cards equal to half the number of cards in their library and loses half their life. Round up each time.

Harsh Mentor

Whenever an opponent activates an ability of an artifact, creature, or land on the battlefield, if it isn't a mana ability, Harsh Mentor deals 2 damage to that player.

Treasonous Ogre

Dethrone (Whenever this creature attacks the player with the most life or tied for most life, put a +1/+1 counter on it.)
Pay 3 life: Add {R}.

Mountain

Blasphemous Act

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

Diabolic Tutor

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

Mind Stone

{T}: Add {C}.
{1}, {T}, Sacrifice Mind Stone: Draw a card.

Fraying Omnipotence

Each player loses half their life, then discards half the cards in their hand, then sacrifices half the creatures they control of their choice. Round up each time.

Wound Reflection

At the beginning of each end step, each opponent loses life equal to the life they lost this turn. (Damage causes loss of life.)

Liliana Vess

+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.

Dark Ritual

Stranglehold

Your opponents can't search libraries.
If an opponent would begin an extra turn, that player skips that turn instead.

Angrath, the Flame-Chained

+1: Each opponent discards a card and loses 2 life.
−3: Gain control of target creature until end of turn. Untap it. It gains haste until end of turn. Sacrifice it at the beginning of the next end step if it has mana value 3 or less.
−8: Each opponent loses life equal to the number of cards in their graveyard.

Smoldering Marsh

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

Maralen of the Mornsong

Players can't draw cards.
At the beginning of each player's draw step, that player loses 3 life, searches their library for a card, puts it into their hand, then shuffles.

Solemn Simulacrum

When this creature enters, you may search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.
When this creature dies, you may draw a card.

Dictate of the Twin Gods

Flash
If a source would deal damage to a permanent or player, it deals double that damage to that permanent or player instead.

Heartless Hidetsugu

{T}: Heartless Hidetsugu deals damage to each player equal to half that player's life total, rounded down.

Evolving Wilds

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

Mindcrank

Whenever an opponent loses life, that player mills that many cards. (Damage causes loss of life.)

Dragonskull Summit

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

Tree of Perdition

Defender
{T}: Exchange target opponent's life total with Tree of Perdition's toughness.

Sorin Markov

+2: Sorin Markov deals 2 damage to any target and you gain 2 life.
−3: Target opponent's life total becomes 10.
−7: You control target player during that player's next turn.

Behold the Beyond

Discard your hand. Search your library for three cards, put them into your hand, then shuffle.

Arcane Signet

Sol Ring

Furnace of Rath

If a source would deal damage to a permanent or player, it deals double that damage to that permanent or player instead.