Spontaneous Mutation

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

Have

Mantle of Tides

Equipped creature gets +1/+2.
Whenever you draw your second card each turn, attach Mantle of Tides to target creature you control.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

World-Weary

Enchant creature
Enchanted creature gets -4/-4.
Basic landcycling {1}{B} ({1}{B}, Discard this card: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.)

Jalum Tome

{2}, {T}: Draw a card, then discard a card.

Ichthyomorphosis

Enchant creature
Enchanted creature loses all abilities and is a blue Fish with base power and toughness 0/1.

Ghastly Demise

Destroy target nonblack creature if its toughness is less than or equal to the number of cards in your graveyard.

Anowon, the Ruin Thief

Other Rogues you control get +1/+1.
Whenever one or more Rogues you control deal combat damage to a player, that player mills a card for each 1 damage dealt to them. If the player mills at least one creature card this way, you draw a card. (To mill a card, a player puts the top card of their library into their graveyard.)

Run Away Together

Choose two target creatures controlled by different players. Return those creatures to their owners' hands.

Galestrike

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

Shortcut Seeker

Whenever Shortcut Seeker deals combat damage to a player, venture into the dungeon. (Enter the first room or advance to the next room.)

Assassinate

So Tiny

Flash
Enchant creature
Enchanted creature gets -2/-0. It gets -6/-0 instead as long as its controller has seven or more cards in their graveyard.

Anticognition

Counter target creature or planeswalker spell unless its controller pays {2}. If an opponent has eight or more cards in their graveyard, instead counter that spell, then scry 2.

Bloodsoaked Altar

{T}, Pay 2 life, Discard a card, Sacrifice a creature: Create a 5/5 black Demon creature token with flying. Activate only as a sorcery.

Draugr Thought-Thief

When Draugr Thought-Thief enters the battlefield, look at the top card of target player's library. You may put that card into their graveyard.

Zulaport Duelist

Flash
When Zulaport Duelist enters the battlefield, up to one target creature gets -2/-0 until end of turn. Its controller mills two cards. (They put the top two cards of their library into their graveyard.)

Corpse Churn

Mill three cards, then you may return a creature card from your graveyard to your hand. (To mill three cards, put the top three cards of your library into your graveyard.)

Rathi Trapper

Latchkey Faerie

Flying
Prowl {2}{U} (You may cast this for its prowl cost if you dealt combat damage to a player this turn with a Faerie or Rogue.)
When Latchkey Faerie enters the battlefield, if its prowl cost was paid, draw a card.

Crippling Chill

Tap target creature. It doesn't untap during its controller's next untap step.
Draw a card.

Metropolis Sprite

Flying
{U}: Metropolis Sprite gets +1/-1 until end of turn.

Bladebrand

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

Dhund Operative

As long as you control an artifact, Dhund Operative gets +1/+0 and has deathtouch.

Infiltrator il-Kor

Shadow (This creature can block or be blocked by only creatures with shadow.)
Suspend 2—{1}{U} (Rather than cast this card from your hand, you may pay {1}{U} and exile it with two time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost. It has haste.)

Withercrown

Enchant creature
Enchanted creature has base power 0 and has "At the beginning of your upkeep, you lose 1 life unless you sacrifice this creature."

Mystic Redaction

At the beginning of your upkeep, scry 1.
Whenever you discard a card, each opponent mills two cards. (They put the top two cards of their library into their graveyard.)

Swamp

Bitter Revelation

Look at the top four cards of your library. Put two of them into your hand and the rest into your graveyard. You lose 2 life.

Sure-Footed Infiltrator

Tap another untapped Rogue you control: Sure-Footed Infiltrator can't be blocked this turn.
Whenever Sure-Footed Infiltrator deals combat damage to a player, draw a card.

Stealer of Secrets

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

Expedition Skulker

Expedition Skulker has deathtouch as long as you control another Rogue.

Sift

Island

Riptide Pilferer

Whenever Riptide Pilferer deals combat damage to a player, that player discards a card.
Morph {U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

Audacious Thief

Whenever Audacious Thief attacks, you draw a card and you lose 1 life.

Capture Sphere

Flash (You may cast this spell any time you could cast an instant.)
Enchant creature
When Capture Sphere enters the battlefield, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

Soul Salvage

Return up to two target creature cards from your graveyard to your hand.

Weigh Down

As an additional cost to cast this spell, exile a creature card from your graveyard.
Target creature gets -3/-3 until end of turn.

Temple Thief

Temple Thief can't be blocked by enchanted creatures or enchantment creatures.

Annul

Counter target artifact or enchantment spell.

Coral Trickster

Morph {U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)
When Coral Trickster is turned face up, you may tap or untap target permanent.

Ior Ruin Expedition

Landfall — Whenever a land enters the battlefield under your control, you may put a quest counter on Ior Ruin Expedition.
Remove three quest counters from Ior Ruin Expedition and sacrifice it: Draw two cards.

Read the Tides

Choose one —
• Draw three cards.
• Return up to two target creatures to their owners' hands.

Blood Beckoning

Kicker {3} (You may pay an additional {3} as you cast this spell.)
Return target creature card from your graveyard to your hand. If this spell was kicked, instead return two target creature cards from your graveyard to your hand.

Frost Breath

Tap up to two target creatures. Those creatures don't untap during their controller's next untap step.

Nimana Skydancer

Flash
Flying
When Nimana Skydancer enters the battlefield, target opponent mills two cards. (They put the top two cards of their library into their graveyard.)

Mental Journey

Draw three cards.
Basic landcycling {1}{U} ({1}{U}, Discard this card: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.)

Undersea Invader

Flash
Undersea Invader enters the battlefield tapped.

Keymaster Rogue

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

Nimana Skitter-Sneak

As long as an opponent has eight or more cards in their graveyard, Nimana Skitter-Sneak gets +1/+0 and has menace. (It can't be blocked except by two or more creatures.)

Moonlit Scavengers

When Moonlit Scavengers enters the battlefield, if you control an artifact or enchantment, return target creature an opponent controls to its owner's hand.

Shadow Stinger

Tap another untapped Rogue you control: Shadow Stinger gains deathtouch until end of turn.
Whenever Shadow Stinger deals combat damage to a player, that player mills three cards. (They put the top three cards of their library into their graveyard.)

Mind Rot

Soulknife Spy

Whenever Soulknife Spy deals combat damage to a player, draw a card.

Ghoulcaller's Accomplice

{3}{B}, Exile Ghoulcaller's Accomplice from your graveyard: Create a 2/2 black Zombie creature token. Activate only as a sorcery.

Brinebarrow Intruder

Flash
When Brinebarrow Intruder enters the battlefield, target creature an opponent controls gets -2/-0 until end of turn.

Memory Drain

Infernal Scarring

Enchant creature
Enchanted creature gets +2/+0 and has "When this creature dies, draw a card."

Mindstab

Target player discards three cards.
Suspend 4—{B} (Rather than cast this card from your hand, you may pay {B} and exile it with four time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost.)

Library Larcenist

Whenever Library Larcenist attacks, draw a card.

Blood Burglar

As long as it's your turn, Blood Burglar has lifelink. (Damage dealt by this creature also causes you to gain that much life.)

Gilt-Blade Prowler

{1}, {T}, Pay 1 life: Draw a card. Activate only if you've discarded a card this turn.

Relic Runner

Relic Runner can't be blocked if you've cast a historic spell this turn. (Artifacts, legendaries, and Sagas are historic.)