Drowned Secrets

Whenever you cast a blue spell, target player mills two cards.

Dimir Guildgate

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

Severed Strands

As an additional cost to cast this spell, sacrifice a creature.
You gain life equal to the sacrificed creature's toughness. Destroy target creature an opponent controls.

Dark Ritual

Strionic Resonator

{2}, {T}: Copy target triggered ability you control. You may choose new targets for the copy. (A triggered ability uses the words "when," "whenever," or "at.")

Macabre Waltz

Return up to two target creature cards from your graveyard to your hand, then discard a card.

Rush of Vitality

Target creature gets +1/+0 and gains lifelink and indestructible until end of turn. (Damage dealt by that creature also causes its controller to gain that much life, and it can't be destroyed by damage or effects that say "destroy.")

Furtive Homunculus

Skulk (This creature can't be blocked by creatures with greater power.)

Contract Killing

Destroy target creature. Create two Treasure tokens. (They're artifacts with "{T}, Sacrifice this artifact: Add one mana of any color.")

Sift

Mari, the Killing Quill

Whenever a creature an opponent controls dies, exile it with a hit counter on it.
Assassins, Mercenaries, and Rogues you control have deathtouch and "Whenever this creature deals combat damage to a player, you may remove a hit counter from a card that player owns in exile. If you do, draw a card and create two Treasure tokens."

Flight

Enchant creature
Enchanted creature has flying.

Control Magic

Enchant creature
You control enchanted creature.

Farbog Revenant

Skulk (This creature can't be blocked by creatures with greater power.)
Lifelink (Damage dealt by this creature also causes you to gain that much life.)

Bartizan Bats

Flying (This creature can't be blocked except by creatures with flying or reach.)

Keeper of Keys

When Keeper of Keys enters, you become the monarch.
At the beginning of your upkeep, if you're the monarch, creatures you control can't be blocked this turn.

Dimir Cluestone

{T}: Add {U} or {B}.
{U}{B}, {T}, Sacrifice Dimir Cluestone: Draw a card.

Lithoform Engine

{2}, {T}: Copy target activated or triggered ability you control. You may choose new targets for the copy.
{3}, {T}: Copy target instant or sorcery spell you control. You may choose new targets for the copy.
{4}, {T}: Copy target permanent spell you control. (The copy becomes a token.)

Deny Existence

Counter target creature spell. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

Skeleton Key

Equipped creature has skulk. (It can't be blocked by creatures with greater power.)
Whenever equipped creature deals combat damage to a player, you may draw a card. If you do, discard a card.
Equip {2}

Counterspell

Leapfrog

Leapfrog has flying as long as you've cast an instant or sorcery spell this turn.

Psychic Venom

Enchant land
Whenever enchanted land becomes tapped, Psychic Venom deals 2 damage to that land's controller.

Walk the Plank

Vicious Conquistador

Whenever Vicious Conquistador attacks, each opponent loses 1 life.

Devious Cover-Up

Counter target spell. If that spell is countered this way, exile it instead of putting it into its owner's graveyard. You may shuffle up to four target cards from your graveyard into your library.

Reave Soul

Destroy target creature with power 3 or less.

Copy Artifact

You may have Copy Artifact enter as a copy of any artifact on the battlefield, except it's an enchantment in addition to its other types.

Wall of Mist

Abnormal Endurance

Until end of turn, target creature gets +2/+0 and gains "When this creature dies, return it to the battlefield tapped under its owner's control."

Unctus, Grand Metatect

Other blue creatures you control have "Whenever this creature becomes tapped, draw a card, then discard a card."
Other artifact creatures you control get +1/+1.
{U/P}: Until end of turn, target creature you control becomes a blue artifact in addition to its other colors and types. Activate only as a sorcery. ({U/P} can be paid with either {U} or 2 life.)

Ravenloft Adventurer

When Ravenloft Adventurer enters, you take the initiative.
If a creature an opponent controls would die, instead exile it and put a hit counter on it.
Whenever Ravenloft Adventurer attacks, if you've completed a dungeon, defending player loses 1 life for each card they own in exile with a hit counter on it.

Unholy Strength

Enchant creature
Enchanted creature gets +2/+1.

Force of Negation

If it's not your turn, you may exile a blue card from your hand rather than pay this spell's mana cost.
Counter target noncreature spell. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

Ghoulsteed

{2}{B}, Discard two cards: Return Ghoulsteed from your graveyard to the battlefield tapped.

Helm of the Host

At the beginning of combat on your turn, create a token that's a copy of equipped creature, except the token isn't legendary. That token gains haste.
Equip {5}

Divination

Mind Twist

Target player discards X cards at random.

Reconstruction

Return target artifact card from your graveyard to your hand.

Etrata, the Silencer

Etrata, the Silencer can't be blocked.
Whenever Etrata deals combat damage to a player, exile target creature that player controls and put a hit counter on that card. That player loses the game if they own three or more exiled cards with hit counters on them. Etrata's owner shuffles Etrata into their library.

Moment of Craving

Target creature gets -2/-2 until end of turn. You gain 2 life.

Diminish

Target creature has base power and toughness 1/1 until end of turn.

Dwindle

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

Drudge Skeletons

{B}: Regenerate Drudge Skeletons. (The next time this creature would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

Steal Artifact

Enchant artifact
You control enchanted artifact.

Swamp

Jace, Ingenious Mind-Mage

+1: Draw a card.
+1: Untap all creatures you control.
−9: Gain control of up to three target creatures.

Burglar Rat

When this creature enters, each opponent discards a card.

Dreamstone Hedron

{T}: Add {C}{C}{C}.
{3}, {T}, Sacrifice Dreamstone Hedron: Draw three cards.

Unwind

Counter target noncreature spell. Untap up to three lands.

Hedron Archive

{T}: Add {C}{C}.
{2}, {T}, Sacrifice this artifact: Draw two cards.

Insidious Bookworms

When Insidious Bookworms dies, you may pay {1}{B}. If you do, target player discards a card at random.

Disdainful Stroke

Counter target spell with mana value 4 or greater.

Wild-Field Scarecrow

Defender
{2}, Sacrifice Wild-Field Scarecrow: Search your library for up to two basic land cards, reveal them, put them into your hand, then shuffle.

Darkslick Shores

Darkslick Shores enters tapped unless you control two or fewer other lands.
{T}: Add {U} or {B}.

Stronghold Confessor

Kicker {3} (You may pay an additional {3} as you cast this spell.)
Menace (This creature can't be blocked except by two or more creatures.)
If Stronghold Confessor was kicked, it enters with two +1/+1 counters on it.

Spell Pierce

Counter target noncreature spell unless its controller pays {2}.

Duress

Target opponent reveals their hand. You choose a noncreature, nonland card from it. That player discards that card.

Cancel

Precognition Field

You may look at the top card of your library any time.
You may cast instant and sorcery spells from the top of your library.
{3}: Exile the top card of your library.

Mnemonic Betrayal

Exile all opponents' graveyards. You may cast spells from among those cards this turn, and mana of any type can be spent to cast them. At the beginning of the next end step, if any of those cards remain exiled, return them to their owners' graveyards.
Exile Mnemonic Betrayal.

Submerged Boneyard

Submerged Boneyard enters tapped.
{T}: Add {U} or {B}.

Silent Observer

High Tide

Until end of turn, whenever a player taps an Island for mana, that player adds an additional {U}.

Eviscerate

Power Leak

Enchant enchantment
At the beginning of the upkeep of enchanted enchantment's controller, that player may pay any amount of mana. Power Leak deals 2 damage to that player. Prevent X of that damage, where X is the amount of mana that player paid this way.

Unimpeded Trespasser

Uninvited Geist

Skulk (This creature can't be blocked by creatures with greater power.)
When Uninvited Geist deals combat damage to a player, transform it.

Uninvited Geist // Unimpeded Trespasser

Island

Sewers of Estark

Choose target creature. If it's attacking, it can't be blocked this turn. If it's blocking, prevent all combat damage that would be dealt this combat by it and each creature it's blocking.