Theater of Horrors

At the beginning of your upkeep, exile the top card of your library.
During your turn, if an opponent lost life this turn, you may play lands and cast spells from among cards exiled with Theater of Horrors.
{3}{R}: Theater of Horrors deals 1 damage to target opponent or planeswalker.

Growth-Chamber Guardian

{2}{G}: Adapt 2. (If this creature has no +1/+1 counters on it, put two +1/+1 counters on it.)
Whenever one or more +1/+1 counters are put on Growth-Chamber Guardian, you may search your library for a card named Growth-Chamber Guardian, reveal it, put it into your hand, then shuffle.

Faerie Duelist

Flash
Flying
When Faerie Duelist enters, target creature an opponent controls gets -2/-0 until end of turn.

Gates Ablaze

Gates Ablaze deals X damage to each creature, where X is the number of Gates you control.

Absorb

Essence Capture

Counter target creature spell. Put a +1/+1 counter on up to one target creature you control.

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.)

Sphinx of New Prahv

Flying, vigilance
Spells your opponents cast that target Sphinx of New Prahv cost {2} more to cast.

Carnage

Carnage deals 3 damage to target opponent. That player discards two cards.

Carnival

Carnival deals 1 damage to target creature or planeswalker and 1 damage to that permanent's controller.

Carnival // Carnage

Plague Wight

Whenever Plague Wight becomes blocked, each creature blocking it gets -1/-1 until end of turn.

Syndicate Guildmage

{1}{W}, {T}: Tap target creature with power 4 or greater.
{4}{B}, {T}: Syndicate Guildmage deals 2 damage to target opponent or planeswalker.

Simic Locket

{T}: Add {G} or {U}.
{G/U}{G/U}{G/U}{G/U}, {T}, Sacrifice Simic Locket: Draw two cards.

Gruul Guildgate

Gruul Guildgate enters tapped.
{T}: Add {R} or {G}.

Steeple Creeper

{3}{U}: Steeple Creeper gains flying until end of turn.

Biomancer's Familiar

Activated abilities of creatures you control cost {2} less to activate. This effect can't reduce the mana in that cost to less than one mana.
{T}: The next time target creature adapts this turn, it adapts as though it had no +1/+1 counters on it.

Tithe Taker

During your turn, spells your opponents cast cost {1} more to cast and abilities your opponents activate cost {1} more to activate unless they're mana abilities.
Afterlife 1 (When this creature dies, create a 1/1 white and black Spirit creature token with flying.)

Vizkopa Vampire

Civic Stalwart

When Civic Stalwart enters, creatures you control get +1/+1 until end of turn.

Rubblebelt Runner

Rubblebelt Runner can't be blocked by creature tokens.

Orzhov Enforcer

Deathtouch
Afterlife 1 (When this creature dies, create a 1/1 white and black Spirit creature token with flying.)

Act of Treason

Gain control of target creature until end of turn. Untap that creature. It gains haste until end of turn. (It can attack and {T} this turn.)

Cult Guildmage

{3}{B}, {T}: Target player discards a card. Activate only as a sorcery.
{R}, {T}: Cult Guildmage deals 1 damage to target opponent or planeswalker.

Debtors' Transport

Afterlife 2 (When this creature dies, create two 1/1 white and black Spirit creature tokens with flying.)

Bankrupt in Blood

As an additional cost to cast this spell, sacrifice two creatures.
Draw three cards.

Mortify

Gift of Strength

Target creature gets +3/+3 and gains reach until end of turn.

Cry of the Carnarium

All creatures get -2/-2 until end of turn. Exile all creature cards in all graveyards that were put there from the battlefield this turn. If a creature would die this turn, exile it instead.

Azorius Locket

{T}: Add {W} or {U}.
{W/U}{W/U}{W/U}{W/U}, {T}, Sacrifice Azorius Locket: Draw two cards.

Swirling Torrent

Choose one or both —
• Put target creature on top of its owner's library.
• Return target creature to its owner's hand.

Chillbringer

Flying
When Chillbringer enters, tap target creature an opponent controls. It doesn't untap during its controller's next untap step.

Imperious Oligarch

Vigilance
Afterlife 1 (When this creature dies, create a 1/1 white and black Spirit creature token with flying.)

Incongruity

Exile target creature. That creature's controller creates a 3/3 green Frog Lizard creature token.

Incubation

Look at the top five cards of your library. You may reveal a creature card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

Incubation // Incongruity

Hero of Precinct One

Whenever you cast a multicolored spell, create a 1/1 white Human creature token.

Immolation Shaman

Whenever an opponent activates an ability of an artifact, creature, or land that isn't a mana ability, Immolation Shaman deals 1 damage to that player.
{3}{R}{R}: Immolation Shaman gets +3/+3 and gains menace until end of turn.

Bolrac-Clan Crusher

{T}, Remove a +1/+1 counter from a creature you control: Bolrac-Clan Crusher deals 2 damage to any target.

Spear Spewer

Defender
{T}: Spear Spewer deals 1 damage to each player.

Forbidding Spirit

When Forbidding Spirit enters, until your next turn, creatures can't attack you or planeswalkers you control unless their controller pays {2} for each of those creatures.

Zhur-Taa Goblin

Riot (This creature enters with your choice of a +1/+1 counter or haste.)

Scrabbling Claws

{T}: Target player exiles a card from their graveyard.
{1}, Sacrifice Scrabbling Claws: Exile target card from a graveyard. Draw a card.

Sky Tether

Enchant creature
Enchanted creature has defender and loses flying.

Storm Strike

Target creature gets +1/+0 and gains first strike until end of turn. Scry 1.

Light Up the Stage

Spectacle {R} (You may cast this spell for its spectacle cost rather than its mana cost if an opponent lost life this turn.)
Exile the top two cards of your library. Until the end of your next turn, you may play those cards.

Ghor-Clan Wrecker

Riot (This creature enters with your choice of a +1/+1 counter or haste.)
Menace (This creature can't be blocked except by two or more creatures.)

Coral Commando

Noxious Groodion

Sharktocrab

{2}{G}{U}: Adapt 1. (If this creature has no +1/+1 counters on it, put a +1/+1 counter on it.)
Whenever one or more +1/+1 counters are put on Sharktocrab, tap target creature an opponent controls. That creature doesn't untap during its controller's next untap step.

Precognitive Perception

Draw three cards.
Addendum — If you cast this spell during your main phase, instead scry 3, then draw three cards.

Senate Guildmage

{W}, {T}: You gain 2 life.
{U}, {T}: Draw a card, then discard a card.

Rakdos Guildgate

Rakdos Guildgate enters tapped.
{T}: Add {B} or {R}.

Frenzied Arynx

Riot (This creature enters with your choice of a +1/+1 counter or haste.)
Trample
{4}{R}{G}: Frenzied Arynx gets +3/+0 until end of turn.

Clear the Stage

Target creature gets -3/-3 until end of turn. If you control a creature with power 4 or greater, you may return up to one target creature card from your graveyard to your hand.

Spirit of the Spires

Flying
Other creatures you control with flying get +0/+1.

Titanic Brawl

This spell costs {1} less to cast if it targets a creature you control with a +1/+1 counter on it.
Target creature you control fights target creature you don't control. (Each deals damage equal to its power to the other.)

Hackrobat

Spectacle {B}{R} (You may cast this spell for its spectacle cost rather than its mana cost if an opponent lost life this turn.)
{B}: Hackrobat gains deathtouch until end of turn.
{R}: Hackrobat gets +2/-2 until end of turn.

Sauroform Hybrid

{4}{G}{G}: Adapt 4. (If this creature has no +1/+1 counters on it, put four +1/+1 counters on it.)

Smothering Tithe

Whenever an opponent draws a card, that player may pay {2}. If the player doesn't, you create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Wrecking Beast

Riot (This creature enters with your choice of a +1/+1 counter or haste.)
Trample

Colossus

Target creature gets +4/+2 and gains trample until end of turn.

Collision

Collision deals 6 damage to target creature with flying.

Collision // Colossus

Clan Guildmage

{1}{R}, {T}: Target creature can't block this turn.
{2}{G}, {T}: Target land you control becomes a 4/4 Elemental creature with haste until end of turn. It's still a land.

Footlight Fiend

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

Orzhov Locket

{T}: Add {W} or {B}.
{W/B}{W/B}{W/B}{W/B}, {T}, Sacrifice Orzhov Locket: Draw two cards.

Scorchmark

Scorchmark deals 2 damage to target creature. If that creature would die this turn, exile it instead.

Tower Defense

Creatures you control get +0/+5 and gain reach until end of turn.

Persistent Petitioners

{1}, {T}: Target player mills a card. (They put the top card of their library into their graveyard.)
Tap four untapped Advisors you control: Target player mills twelve cards.
A deck can have any number of cards named Persistent Petitioners.

Bladebrand

Target creature gains deathtouch until end of turn.
Draw a card.

Rubblebelt Recluse

Rubblebelt Recluse attacks each combat if able.

Senate Griffin

Flying
When Senate Griffin enters, scry 1.

Arrester's Admonition

Return target creature to its owner's hand.
Addendum — If you cast this spell during your main phase, draw a card.

Skitter Eel

{2}{U}: Adapt 2. (If this creature has no +1/+1 counters on it, put two +1/+1 counters on it.)

Amplifire

At the beginning of your upkeep, reveal cards from the top of your library until you reveal a creature card. Until your next turn, Amplifire's base power becomes twice that card's power and its base toughness becomes twice that card's toughness. Put the revealed cards on the bottom of your library in a random order.

Trollbred Guardian

{2}{G}: Adapt 2. (If this creature has no +1/+1 counters on it, put two +1/+1 counters on it.)
Each creature you control with a +1/+1 counter on it has trample.

Slimebind

Flash
Enchant creature
Enchanted creature gets -4/-0.

Thirsting Shade

Lifelink
{2}{B}: Thirsting Shade gets +1/+1 until end of turn.

Clamor Shaman

Riot (This creature enters with your choice of a +1/+1 counter or haste.)
Whenever Clamor Shaman attacks, target creature an opponent controls can't block this turn.

Syndicate Messenger

Flying
Afterlife 1 (When this creature dies, create a 1/1 white and black Spirit creature token with flying.)

Undercity Scavenger

When Undercity Scavenger enters, you may sacrifice another creature. If you do, put two +1/+1 counters on Undercity Scavenger, then scry 2.

Carrion Imp

Flying
When Carrion Imp enters, you may exile target creature card from a graveyard. If you do, you gain 2 life.

Breeding Pool

({T}: Add {G} or {U}.)
As Breeding Pool enters, you may pay 2 life. If you don't, it enters tapped.

Screaming Shield

Equipped creature gets +0/+3 and has "{2}, {T}: Target player mills three cards."
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

End-Raze Forerunners

Vigilance, trample, haste
When End-Raze Forerunners enters, other creatures you control get +2/+2 and gain vigilance and trample until end of turn.

Gateway Plaza

Gateway Plaza enters tapped.
When Gateway Plaza enters, sacrifice it unless you pay {1}.
{T}: Add one mana of any color.

Skatewing Spy

{5}{U}: Adapt 2. (If this creature has no +1/+1 counters on it, put two +1/+1 counters on it.)
Each creature you control with a +1/+1 counter on it has flying.

Bedazzle

Destroy target nonbasic land. Bedazzle deals 2 damage to target opponent or planeswalker.

Bedeck

Target creature gets +3/-3 until end of turn.

Bedeck // Bedazzle

Justiciar's Portal

Exile target creature you control, then return that card to the battlefield under its owner's control. It gains first strike until end of turn.

Quench

Counter target spell unless its controller pays {2}.

Rubble Reading

Gravel-Hide Goblin

{3}{G}: Gravel-Hide Goblin gets +2/+2 until end of turn.

Twilight Panther

{B}: Twilight Panther gains deathtouch until end of turn.

Azorius Skyguard

Flying, first strike
Creatures your opponents control get -1/-0.

Growth Spiral

Draw a card. You may put a land card from your hand onto the battlefield.

Mirror March

Whenever a nontoken creature you control enters, flip a coin until you lose a flip. For each flip you won, create a token that's a copy of that creature. Those tokens gain haste. Exile them at the beginning of the next end step.

Skarrgan Hellkite

Riot (This creature enters with your choice of a +1/+1 counter or haste.)
Flying
{3}{R}: Skarrgan Hellkite deals 2 damage divided as you choose among one or two targets. Activate only if Skarrgan Hellkite has a +1/+1 counter on it.

Dagger Caster

When Dagger Caster enters, it deals 1 damage to each opponent and 1 damage to each creature your opponents control.

Emergency Powers

Each player shuffles their hand and graveyard into their library, then draws seven cards. Exile Emergency Powers.
Addendum — If you cast this spell during your main phase, you may put a permanent card with mana value 7 or less from your hand onto the battlefield.

Vindictive Vampire

Whenever another creature you control dies, Vindictive Vampire deals 1 damage to each opponent and you gain 1 life.

Axebane Beast

Lawmage's Binding

Flash
Enchant creature
Enchanted creature can't attack or block, and its activated abilities can't be activated.

Cavalcade of Calamity

Whenever a creature you control with power 1 or less attacks, Cavalcade of Calamity deals 1 damage to the player or planeswalker that creature is attacking.