Spontaneous Mutation

Flash
Enchant creature
Enchanted creature gets -X/-0, where X is the number of cards in your graveyard.

Disperse

Return target nonland permanent to its owner's hand.

Runewing

Doorkeeper

Defender
{2}{U}, {T}: Target player mills X cards, where X is the number of creatures you control with defender.

Aviation Pioneer

When Aviation Pioneer enters, create a 1/1 colorless Thopter artifact creature token with flying.

Jace's Phantasm

Flying
Jace's Phantasm gets +4/+4 as long as an opponent has ten or more cards in their graveyard.

Drag Under

Return target creature to its owner's hand.
Draw a card.

Countervailing Winds

Counter target spell unless its controller pays {1} for each card in your graveyard.
Cycling {2} ({2}, Discard this card: Draw a card.)

Soulsworn Spirit

Soulsworn Spirit can't be blocked.
When Soulsworn Spirit enters, detain target creature an opponent controls. (Until your next turn, that creature can't attack or block and its activated abilities can't be activated.)

Dwindle

Enchant creature
Enchanted creature gets -6/-0.
When enchanted creature blocks, destroy it. (The attacking creature remains blocked.)

Kraken of the Straits

Creatures with power less than the number of Islands you control can't block Kraken of the Straits.

Horizon Scholar

Flying
When Horizon Scholar enters, scry 2. (Look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Turn Aside

Counter target spell that targets a permanent you control.

Wind Drake

Sphinx of the Chimes

Flying
Discard two nonland cards with the same name: Draw four cards.

Voidwielder

When Voidwielder enters, you may return target creature to its owner's hand.

Sapphire Drake

Flying
Each creature you control with a +1/+1 counter on it has flying.

Spell Rupture

Counter target spell unless its controller pays {X}, where X is the greatest power among creatures you control.

Dispel

Enlightened Maniac

When Enlightened Maniac enters, create a 3/2 colorless Eldrazi Horror creature token.

Aetherize

Return all attacking creatures to their owner's hand.

Enclave Elite

Multikicker {1}{U} (You may pay an additional {1}{U} any number of times as you cast this spell.)
Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Enclave Elite enters with a +1/+1 counter on it for each time it was kicked.

Imaginary Threats

Creatures target opponent controls attack this turn if able. During that player's next untap step, creatures they control don't untap.
Cycling {2} ({2}, Discard this card: Draw a card.)

Keymaster Rogue

Keymaster Rogue can't be blocked.
When Keymaster Rogue enters, return a creature you control to its owner's hand.

Anticipate

Look at the top three cards of your library. Put one of them into your hand and the rest on the bottom of your library in any order.

Thassa's Bounty

Draw three cards. Target player mills three cards.

Paralyzing Grasp

Enchant creature
Enchanted creature doesn't untap during its controller's untap step.

Divination

Essence Scatter

Aquus Steed

{2}{U}, {T}: Target creature gets -2/-0 until end of turn.

Scatter Arc

Counter target noncreature spell.
Draw a card.

Vedalken Entrancer

Shimmerscale Drake

Flying
Cycling {2} ({2}, Discard this card: Draw a card.)

Blustersquall

Tap target creature you don't control.
Overload {3}{U} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Stealer of Secrets

Whenever Stealer of Secrets deals combat damage to a player, draw a card.

Weight of Memory

Cancel

Seer of the Last Tomorrow

{U}, {T}, Discard a card: Target player mills three cards.

Calcite Snapper

Shroud (This creature can't be the target of spells or abilities.)
Landfall — Whenever a land you control enters, you may switch Calcite Snapper's power and toughness until end of turn.

Cloudfin Raptor

Flying
Evolve (Whenever a creature you control enters, if that creature has greater power or toughness than this creature, put a +1/+1 counter on this creature.)

Aven Reedstalker

Kraken Hatchling

Salvager of Secrets

When Salvager of Secrets enters, return target instant or sorcery card from your graveyard to your hand.

Switcheroo

Exchange control of two target creatures.

Hieroglyphic Illumination

Draw two cards.
Cycling {U} ({U}, Discard this card: Draw a card.)

Surrakar Banisher

When Surrakar Banisher enters, you may return target tapped creature to its owner's hand.

Deadeye Rig-Hauler

Raid — When Deadeye Rig-Hauler enters, if you attacked this turn, you may return target creature to its owner's hand.

Geist of the Archives

Defender
At the beginning of your upkeep, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Striped Riverwinder

Hexproof (This creature can't be the target of spells or abilities your opponents control.)
Cycling {U} ({U}, Discard this card: Draw a card.)

Sphinx's Disciple

Flying
Inspired — Whenever Sphinx's Disciple becomes untapped, draw a card.

Simic Fluxmage

Evolve (Whenever a creature you control enters, if that creature has greater power or toughness than this creature, put a +1/+1 counter on this creature.)
{1}{U}, {T}: Move a +1/+1 counter from Simic Fluxmage onto target creature.

Messenger Drake

Flying
When Messenger Drake dies, draw a card.

Mind Sculpt

Voidwalk

Exile target creature. Return it to the battlefield under its owner's control at the beginning of the next end step.
Cipher (Then you may exile this spell card encoded on a creature you control. Whenever that creature deals combat damage to a player, its controller may cast a copy of the encoded card without paying its mana cost.)

Wavecrash Triton

Heroic — Whenever you cast a spell that targets Wavecrash Triton, tap target creature an opponent controls. That creature doesn't untap during its controller's next untap step.

Unsummon

Return target creature to its owner's hand.

Frilled Oculus

{1}{G}: Frilled Oculus gets +2/+2 until end of turn. Activate only once each turn.

Labyrinth Guardian

When Labyrinth Guardian becomes the target of a spell, sacrifice it.
Embalm {3}{U} ({3}{U}, Exile this card from your graveyard: Create a token that's a copy of it, except it's a white Zombie Illusion Warrior with no mana cost. Embalm only as a sorcery.)

Fated Infatuation

Create a token that's a copy of target creature you control. If it's your turn, scry 2.

Halimar Excavator

Whenever Halimar Excavator or another Ally you control enters, target player mills X cards, where X is the number of Allies you control.

Secrets of the Golden City

Ascend (If you control ten or more permanents, you get the city's blessing for the rest of the game.)
Draw two cards. If you have the city's blessing, draw three cards instead.

Downsize

Target creature you don't control gets -4/-0 until end of turn.
Overload {2}{U} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Hekma Sentinels

Whenever you cycle or discard a card, Hekma Sentinels gets +1/+1 until end of turn.

Mindreaver

Heroic — Whenever you cast a spell that targets Mindreaver, exile the top three cards of target player's library.
{U}{U}, Sacrifice Mindreaver: Counter target spell with the same name as a card exiled with Mindreaver.

Cloudreader Sphinx

Flying
When Cloudreader Sphinx enters, scry 2. (Look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Fortune's Favor

Target opponent looks at the top four cards of your library and separates them into a face-down pile and a face-up pile. Put one pile into your hand and the other into your graveyard.

Cunning Survivor

Whenever you cycle or discard a card, Cunning Survivor gets +1/+0 until end of turn and can't be blocked this turn.

Nullify

Rewind

Counter target spell. Untap up to four lands.

Crypsis

Target creature you control gains protection from creatures your opponents control until end of turn. Untap it.

Curse of Echoes

Enchant player
Whenever enchanted player casts an instant or sorcery spell, each other player may copy that spell and may choose new targets for the copy they control.

Spire Winder

Flying
Ascend (If you control ten or more permanents, you get the city's blessing for the rest of the game.)
Spire Winder gets +1/+1 as long as you have the city's blessing.

Hands of Binding

Tap target creature an opponent controls. That creature doesn't untap during its controller's next untap step.
Cipher (Then you may exile this spell card encoded on a creature you control. Whenever that creature deals combat damage to a player, its controller may cast a copy of the encoded card without paying its mana cost.)

Mist Raven

Flying
When Mist Raven enters, return target creature to its owner's hand.

Prescient Chimera

Flying
Whenever you cast an instant or sorcery spell, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Syncopate

Counter target spell unless its controller pays {X}. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

Ancient Crab

Frilled Sea Serpent

{5}{U}{U}: Frilled Sea Serpent can't be blocked this turn.

Inaction Injunction

Detain target creature an opponent controls. (Until your next turn, that creature can't attack or block and its activated abilities can't be activated.)
Draw a card.

Totally Lost

Put target nonland permanent on top of its owner's library.

Mizzium Skin

Target creature you control gets +0/+1 and gains hexproof until end of turn.
Overload {1}{U} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Conjured Currency

At the beginning of your upkeep, you may exchange control of Conjured Currency and target permanent you neither own nor control.

Vizier of the Anointed

When Vizier of the Anointed enters, you may search your library for a creature card with eternalize or embalm, put that card into your graveyard, then shuffle.
Whenever you activate an eternalize or embalm ability, draw a card.

Opal Lake Gatekeepers

When Opal Lake Gatekeepers enters, if you control two or more Gates, you may draw a card.

Thassa's Rebuff

Counter target spell unless its controller pays {X}, where X is your devotion to blue. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)

Sage's Row Denizen

Whenever another blue creature you control enters, target player mills two cards.

Chorus of the Tides

Flying
Heroic — Whenever you cast a spell that targets Chorus of the Tides, scry 1. (To scry 1, look at the top card of your library, then you may put that card on the bottom.)

Opportunity

Winds of Rebuke

Return target nonland permanent to its owner's hand. Each player mills two cards.

Temporal Machinations

Return target creature to its owner's hand. If you control an artifact, draw a card.

Tragic Lesson

Draw two cards. Then discard a card unless you return a land you control to its owner's hand.

Unwind

Counter target noncreature spell. Untap up to three lands.

Faerie Impostor

Flying
When Faerie Impostor enters, sacrifice it unless you return another creature you control to its owner's hand.

Gryff Vanguard

Flying
When Gryff Vanguard enters, draw a card.

Tattered Haunter

Flying
Tattered Haunter can block only creatures with flying.

Deepwater Hypnotist

Inspired — Whenever Deepwater Hypnotist becomes untapped, target creature an opponent controls gets -3/-0 until end of turn.

Reverse Engineer

Improvise (Your artifacts can help cast this spell. Each artifact you tap after you're done activating mana abilities pays for {1}.)
Draw three cards.

Fogwalker

Skulk (This creature can't be blocked by creatures with greater power.)
When Fogwalker enters, target creature an opponent controls doesn't untap during its controller's next untap step.

Omenspeaker

When Omenspeaker enters, scry 2. (Look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Mnemonic Nexus

Each player shuffles their graveyard into their library.

Leyline Phantom

When Leyline Phantom deals combat damage, return it to its owner's hand. (Return it only if it survived combat.)

Incursion Specialist

Whenever you cast your second spell each turn, Incursion Specialist gets +2/+0 until end of turn and can't be blocked this turn.

Silver Erne

Curator of Mysteries

Flying
Whenever you cycle or discard another card, scry 1.
Cycling {U} ({U}, Discard this card: Draw a card.)

Meletis Astronomer

Heroic — Whenever you cast a spell that targets Meletis Astronomer, look at the top three cards of your library. You may reveal an enchantment card from among them and put it into your hand. Put the rest on the bottom of your library in any order.

Jace's Defeat

Counter target blue spell. If it was a Jace planeswalker spell, scry 2.

River Serpent

River Serpent can't attack unless there are five or more cards in your graveyard.
Cycling {U} ({U}, Discard this card: Draw a card.)

Sudden Storm

Tap up to two target creatures. Those creatures don't untap during their controllers' next untap steps. Scry 1. (Look at the top card of your library. You may put that card on the bottom.)