Prisoner's Dilemma

Each opponent secretly chooses silence or snitch, then the choices are revealed. If each opponent chose silence, Prisoner's Dilemma deals 4 damage to each of them. If each opponent chose snitch, Prisoner's Dilemma deals 8 damage to each of them. Otherwise, Prisoner's Dilemma deals 12 damage to each opponent who chose silence.
Flashback {5}{R}{R}

Treasure

{T}, Sacrifice this token: Add one mana of any color.

Relic Robber

Haste
Whenever this creature deals combat damage to a player, that player creates a 0/1 colorless Goblin Construct artifact creature token with "This token can't block" and "At the beginning of your upkeep, this token deals 1 damage to you."

Swamp

Dark Confidant

At the beginning of your upkeep, reveal the top card of your library and put that card into your hand. You lose life equal to its mana value.

Mountain

Snort

Each player may discard their hand and draw five cards. Then Snort deals 5 damage to each opponent who discarded their hand this way.
Flashback {5}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Descent into Avernus

At the beginning of your upkeep, put two descent counters on this enchantment. Then each player creates X Treasure tokens and this enchantment deals X damage to each player, where X is the number of descent counters on this enchantment.

Mages' Contest

You and target spell's controller bid life. You start the bidding with a bid of 1. In turn order, each player may top the high bid. The bidding ends if the high bid stands. The high bidder loses life equal to the high bid. If you win the bidding, counter that spell.

Plague of Vermin

Starting with you, each player may pay any amount of life. Repeat this process until no one pays life. Each player creates a 1/1 black Rat creature token for each 1 life they paid this way.

Blood Crypt

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

Abyssal Persecutor

Flying, trample
You can't win the game and your opponents can't lose the game.

Fires of Invention

You can cast spells only during your turn and you can cast no more than two spells each turn.
You may cast spells with mana value less than or equal to the number of lands you control without paying their mana costs.

Foreboding Ruins

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

Command Tower

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

Jinxed Choker

At the beginning of your end step, target opponent gains control of this artifact and puts a charge counter on it.
At the beginning of your upkeep, this artifact deals damage to you equal to the number of charge counters on it.
{3}: Put a charge counter on this artifact or remove one from it.

Palantír of Orthanc

At the beginning of your end step, put an influence counter on Palantír of Orthanc and scry 2. Then target opponent may have you draw a card. If that player doesn't, you mill X cards, where X is the number of influence counters on Palantír of Orthanc, and that player loses life equal to the total mana value of those cards.

Goblin Psychopath

Whenever this creature attacks or blocks, flip a coin. If you lose the flip, the next time it would deal combat damage this turn, it deals that damage to you instead.

Lord of the Pit

Flying, trample
At the beginning of your upkeep, sacrifice a creature other than this creature. If you can't, this creature deals 7 damage to you.

Firedrinker Satyr

Whenever this creature is dealt damage, it deals that much damage to you.
{1}{R}: This creature gets +1/+0 until end of turn and deals 1 damage to you.

Smoldering Marsh

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

Pain's Reward

Each player may bid life. You start the bidding with a bid of any number. In turn order, each player may top the high bid. The bidding ends if the high bid stands. The high bidder loses life equal to the high bid and draws four cards.

Bojuka Bog

This land enters tapped.
When this land enters, exile target player's graveyard.
{T}: Add {B}.

Luxury Suite

This land enters tapped unless you have two or more opponents.
{T}: Add {B} or {R}.

Thieves' Auction

Exile all nontoken permanents. Starting with you, each player chooses one of the exiled cards and puts it onto the battlefield tapped under their control. Repeat this process until all cards exiled this way have been chosen.

Goblin Lyre

Sacrifice this artifact: Flip a coin. If you win the flip, this artifact deals damage to target opponent or planeswalker equal to the number of creatures you control. If you lose the flip, this artifact deals damage to you equal to the number of creatures that opponent or that planeswalker's controller controls.

Temple of Malice

This land enters tapped.
When this land enters, scry 1. (Look at the top card of your library. You may put that card on the bottom.)
{T}: Add {B} or {R}.

Wheel of Torture

At the beginning of each opponent's upkeep, this artifact deals X damage to that player, where X is 3 minus the number of cards in their hand.

Bloodfell Caves

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {B} or {R}.

Graf Reaver

Exploit (When this creature enters, you may sacrifice a creature.)
When this creature exploits a creature, destroy target planeswalker.
At the beginning of your upkeep, this creature deals 1 damage to you.

Shinka Gatekeeper

Whenever this creature is dealt damage, it deals that much damage to you.

Blim, Comedic Genius

Flying
Whenever Blim deals combat damage to a player, that player gains control of target permanent you control. Then each player loses life and discards cards equal to the number of permanents they control but don't own.

Sol Ring

Frenzied Gorespawn

When this creature enters, for each opponent, goad target creature that player controls. (Until your next turn, those creatures attack each combat if able and attack a player other than you if able.)
Whenever one or more creatures attack one of your opponents, those creatures gain menace until end of turn.

Gollum, Scheming Guide

Whenever Gollum attacks, look at the top two cards of your library, put them back in any order, then choose land or nonland. An opponent guesses whether the top card of your library is the chosen kind. Reveal that card. If they guessed right, remove Gollum from combat. Otherwise, you draw a card and Gollum can't be blocked this turn.

Rain of Gore

If a spell or ability would cause its controller to gain life, that player loses that much life instead.

Sower of Discord

Flying
As this creature enters, choose two players.
Whenever damage is dealt to one of the chosen players, the other chosen player also loses that much life.

Dark Tutelage

Gray Merchant of Asphodel

When this creature 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.)

Geist-Fueled Scarecrow

Creature spells you cast cost {1} more to cast.

Daily Bugle Building

{T}: Add {C}.
{1}, {T}: Add one mana of any color.
Smear Campaign — {1}, {T}: Target legendary creature gains menace until end of turn. Activate only as a sorcery.

Jinxed Idol

At the beginning of your upkeep, this artifact deals 2 damage to you.
Sacrifice a creature: Target opponent gains control of this artifact.

Flesh Reaver

Whenever this creature deals damage to a creature or opponent, this creature deals that much damage to you.

Goldnight Castigator

Flying, haste
If a source would deal damage to you, it deals double that damage to you instead.
If a source would deal damage to this creature, it deals double that damage to this creature instead.

Silver Shroud Costume

Flash
When this Equipment enters, attach it to target creature you control. That creature gains shroud until end of turn. (It can't be the target of spells or abilities.)
Equipped creature can't be blocked.
Equip {3}

Game of Chaos

Flip a coin. If you win the flip, you gain 1 life and target opponent loses 1 life, and you decide whether to flip again. If you lose the flip, you lose 1 life and that opponent gains 1 life, and that player decides whether to flip again. Double the life stakes with each flip.

Mana Clash

You and target opponent each flip a coin. Mana Clash deals 1 damage to each player whose coin comes up tails. Repeat this process until both players' coins come up heads on the same flip.

Rakdos Cluestone

{T}: Add {B} or {R}.
{B}{R}, {T}, Sacrifice this artifact: Draw a card.

Liege of the Pit

Flying, trample
At the beginning of your upkeep, sacrifice a creature other than this creature. If you can't, this creature deals 7 damage to you.
Morph {B}{B}{B}{B} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

Rakdos Carnarium

This land enters tapped.
When this land enters, return a land you control to its owner's hand.
{T}: Add {B}{R}.

Jackal Pup

Rogue's Passage

{T}: Add {C}.
{4}, {T}: Target creature can't be blocked this turn.

Rakdos Firewheeler

When this creature enters, it deals 2 damage to target opponent and 2 damage to up to one target creature or planeswalker.

Goblin Construct

This creature can't block.
At the beginning of your upkeep, this creature deals 1 damage to you.

Cursed Recording

Whenever you cast an instant or sorcery spell, put a time counter on this artifact. Then if there are seven or more time counters on it, remove those counters and it deals 20 damage to you.
{T}: When you next cast an instant or sorcery spell this turn, copy that spell. You may choose new targets for the copy.

Xantcha, Sleeper Agent

Xantcha enters under the control of an opponent of your choice.
Xantcha attacks each combat if able and can't attack its owner or planeswalkers its owner controls.
{3}: Xantcha's controller loses 2 life and you draw a card. Any player may activate this ability.

Haunted Ridge

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

Illicit Auction

Each player may bid life for control of target creature. You start the bidding with a bid of 0. In turn order, each player may top the high bid. The bidding ends if the high bid stands. The high bidder loses life equal to the high bid and gains control of the creature. (This effect lasts indefinitely.)

Tyrant's Choice

Will of the council — Starting with you, each player votes for death or torture. If death gets more votes, each opponent sacrifices a creature of their choice. If torture gets more votes or the vote is tied, each opponent loses 4 life.

Everlasting Torment

Players can't gain life.
Damage can't be prevented.
All damage is dealt as though its source had wither. (A source with wither deals damage to creatures in the form of -1/-1 counters.)

Tainted Peak

{T}: Add {C}.
{T}: Add {B} or {R}. Activate only if you control a Swamp.

Jinxed Ring

Whenever a nontoken permanent is put into your graveyard from the battlefield, this artifact deals 1 damage to you.
Sacrifice a creature: Target opponent gains control of this artifact. (This effect lasts indefinitely.)

Pendant of Prosperity

This artifact enters under the control of an opponent of your choice.
{2}, {T}: Draw a card, then you may put a land card from your hand onto the battlefield. This artifact's owner draws a card, then that player may put a land card from their hand onto the battlefield.

Dragonskull Summit

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

Spikewheel Acrobat

Spectacle {2}{R} (You may cast this spell for its spectacle cost rather than its mana cost if an opponent lost life this turn.)

Colfenor's Plans

When this enchantment enters, exile the top seven cards of your library face down.
You may look at the cards exiled with this enchantment, and you may play lands and cast spells from among those cards.
Skip your draw step.
You can't cast more than one spell each turn.

The Death of Gwen Stacy

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Destroy target creature.
II — Each player may discard a card. Each player who doesn't loses 3 life.
III — Exile any number of target players' graveyards.

Wheel of Misfortune

Each player secretly chooses a number 0 or greater, then all players reveal those numbers simultaneously and determine the highest and lowest numbers revealed this way. Wheel of Misfortune deals damage equal to the highest number to each player who chose that number. Each player who didn't choose the lowest number discards their hand, then draws seven cards.

Harmless Offering

Target opponent gains control of target permanent you control.

Experimental Frenzy

You may look at the top card of your library any time.
You may play lands and cast spells from the top of your library.
You can't play lands or cast spells from your hand.
{3}{R}: Destroy this enchantment.

Rakdos Signet

Agility Bobblehead

{T}: Add one mana of any color.
{3}, {T}: Up to X target creatures you control each gain haste until end of turn and can't be blocked this turn except by creatures with haste, where X is the number of Bobbleheads you control as you activate this ability.

Steel Golem

Obsidian Fireheart

{1}{R}{R}: Put a blaze counter on target land without a blaze counter on it. For as long as that land has a blaze counter on it, it has "At the beginning of your upkeep, this land deals 1 damage to you." (The land continues to burn after this creature has left the battlefield.)

Choice of Damnations

Target opponent chooses a number. You may have that player lose that much life. If you don't, that player sacrifices all but that many permanents of their choice.

Fledgling Djinn

Flying
At the beginning of your upkeep, this creature deals 1 damage to you.

Rakdos Guildgate

This land enters tapped.
{T}: Add {B} or {R}.

Blood Funnel

Noncreature spells you cast cost {2} less to cast.
Whenever you cast a noncreature spell, counter that spell unless you sacrifice a creature.

The Toymaker's Trap

At the beginning of your upkeep, secretly choose a number between 1 and 5 that hasn't been chosen. If you do, an opponent guesses which number you chose, then you reveal the number you chose. If they guessed wrong, they lose life equal to the number they guessed and you draw a card. If they guessed right, sacrifice this enchantment.

Manifold Key

{1}, {T}: Untap another target artifact.
{3}, {T}: Target creature can't be blocked this turn.

Shizo, Death's Storehouse

{T}: Add {B}.
{B}, {T}: Target legendary creature gains fear until end of turn. (It can't be blocked except by artifact creatures and/or black creatures.)

Sonic Screwdriver

{T}: Add one mana of any color.
{1}, {T}: Untap another target artifact.
{2}, {T}: Scry 1. (Look at the top card of your library. You may put that card on the bottom.)
{3}, {T}: Target creature can't be blocked this turn.