Counterspell

Frantic Search

Draw two cards, then discard two cards. Untap up to three lands.

Thassa's Oracle

When Thassa's Oracle enters, look at the top X cards of your library, where X is your devotion to blue. Put up to one of them on top of your library and the rest on the bottom of your library in a random order. If X is greater than or equal to the number of cards in your library, you win the game. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)

Sol Ring

Agent of Treachery

When Agent of Treachery enters, gain control of target permanent.
At the beginning of your end step, if you control three or more permanents you don't own, draw three cards.

Ghostly Flicker

Exile two target artifacts, creatures, and/or lands you control, then return those cards to the battlefield under your control.

Tome Raider

Flying
When Tome Raider enters, draw a card.

Sower of Temptation

Flying
When Sower of Temptation enters, gain control of target creature for as long as Sower of Temptation remains on the battlefield.

Solemn Simulacrum

When Solemn Simulacrum enters, you may search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.
When Solemn Simulacrum dies, you may draw a card.

Scholar of the Ages

When Scholar of the Ages enters, return up to two target instant and/or sorcery cards from your graveyard to your hand.

Arcane Signet

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

Blue Sun's Zenith

Target player draws X cards. Shuffle Blue Sun's Zenith into its owner's library.

Dig Through Time

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Look at the top seven cards of your library. Put two of them into your hand and the rest on the bottom of your library in any order.

Nyx Lotus

Nyx Lotus enters tapped.
{T}: Choose a color. Add an amount of mana of that color equal to your devotion to that color. (Your devotion to a color is the number of mana symbols of that color in the mana costs of permanents you control.)

Essence Flux

Exile target creature you control, then return that card to the battlefield under its owner's control. If it's a Spirit, put a +1/+1 counter on it.

Venser, Shaper Savant

Flash
When Venser, Shaper Savant enters, return target spell or permanent to its owner's hand.

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.)

Riverwise Augur

When Riverwise Augur enters, draw three cards, then put two cards from your hand on top of your library in any order.

The Magic Mirror

This spell costs {1} less to cast for each instant and sorcery card in your graveyard.
You have no maximum hand size.
At the beginning of your upkeep, put a knowledge counter on The Magic Mirror, then draw a card for each knowledge counter on The Magic Mirror.

Exclusion Mage

When Exclusion Mage enters, return target creature an opponent controls to its owner's hand.

Teferi's Ageless Insight

If you would draw a card except the first one you draw in each of your draw steps, draw two cards instead.

Laboratory Maniac

If you would draw a card while your library has no cards in it, you win the game instead.

Fact or Fiction

Reveal the top five cards of your library. An opponent separates those cards into two piles. Put one pile into your hand and the other into your graveyard.

Siren's Ruse

Exile target creature you control, then return that card to the battlefield under its owner's control. If a Pirate was exiled this way, draw a card.

Fblthp, the Lost

When Fblthp, the Lost enters, draw a card. If it entered from your library or was cast from your library, draw two cards instead.
When Fblthp becomes the target of a spell, shuffle Fblthp into its owner's library.

Man-o'-War

When Man-o'-War enters, return target creature to its owner's hand.

Scourge of Fleets

When Scourge of Fleets enters, return each creature your opponents control with toughness X or less to its owner's hand, where X is the number of Islands you control.

Scroll of Fate

{T}: Manifest a card from your hand. (Put that card onto the battlefield face down as a 2/2 creature. Turn it face up any time for its mana cost if it's a creature card.)

Archaeomancer

When Archaeomancer enters, return target instant or sorcery card from your graveyard to your hand.

Wizard's Retort

This spell costs {1} less to cast if you control a Wizard.
Counter target spell.

Teferi's Time Twist

Exile target permanent you control. Return that card to the battlefield under its owner's control at the beginning of the next end step. If it enters as a creature, it enters with an additional +1/+1 counter on it.

Mind Stone

{T}: Add {C}.
{1}, {T}, Sacrifice Mind Stone: Draw a card.

Chamber of Manipulation

Enchant land
Enchanted land has "{T}, Discard a card: Gain control of target creature until end of turn."

Prismatic Lens

{T}: Add {C}.
{1}, {T}: Add one mana of any color.

Fellwar Stone

{T}: Add one mana of any color that a land an opponent controls could produce.

Planar Incision

Exile target artifact or creature, then return it to the battlefield under its owner's control with a +1/+1 counter on it.

Sea Gate Oracle

When Sea Gate Oracle enters, look at the top two cards of your library. Put one of them into your hand and the other on the bottom of your library.

Circuit Mender

When Circuit Mender enters, you gain 2 life.
When Circuit Mender leaves the battlefield, draw a card.

Vedalken Aethermage

Flash (You may cast this spell any time you could cast an instant.)
When Vedalken Aethermage enters, return target Sliver to its owner's hand.
Wizardcycling {3} ({3}, Discard this card: Search your library for a Wizard card, reveal it, put it into your hand, then shuffle.)

Thassa, Deep-Dwelling

Indestructible
As long as your devotion to blue is less than five, Thassa isn't a creature.
At the beginning of your end step, exile up to one other target creature you control, then return that card to the battlefield under your control.
{3}{U}: Tap another target creature.

Glen Elendra Archmage

Flying
{U}, Sacrifice Glen Elendra Archmage: Counter target noncreature spell.
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Step Through

Return two target creatures to their owners' hands.
Wizardcycling {2} ({2}, Discard this card: Search your library for a Wizard card, reveal it, put it into your hand, then shuffle.)

Master of Waves

Protection from red
Elemental creatures you control get +1/+1.
When Master of Waves enters, create a number of 1/0 blue Elemental creature tokens equal to your devotion to blue. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)

Barrin, Tolarian Archmage

When Barrin, Tolarian Archmage enters, return up to one other target creature or planeswalker to its owner's hand.
At the beginning of your end step, if a permanent was put into your hand from the battlefield this turn, draw a card.

Island

Engulf the Shore

Return to their owners' hands all creatures with toughness less than or equal to the number of Islands you control.

Cloudkin Seer

Flying
When Cloudkin Seer enters, draw a card.

Familiar's Ruse

As an additional cost to cast this spell, return a creature you control to its owner's hand.
Counter target spell.

Duplicant

Imprint — When Duplicant enters, you may exile target nontoken creature.
As long as a card exiled with Duplicant is a creature card, Duplicant has the power, toughness, and creature types of the last creature card exiled with Duplicant. It's still a Shapeshifter.

Mulldrifter

Flying
When Mulldrifter enters, draw two cards.
Evoke {2}{U} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Rite of Replication

Kicker {5} (You may pay an additional {5} as you cast this spell.)
Create a token that's a copy of target creature. If this spell was kicked, create five of those tokens instead.

Wash Away

Cleave {1}{U}{U} (You may cast this spell for its cleave cost. If you do, remove the words in square brackets.)
Counter target spell [that wasn't cast from its owner's hand].

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.")

Peregrine Drake

Flying
When Peregrine Drake enters, untap up to five lands.

Floodgate

Defender
When Floodgate has flying, sacrifice it.
When Floodgate leaves the battlefield, it deals damage to each nonblue creature without flying equal to half the number of Islands you control, rounded down.

Callaphe, Beloved of the Sea

Callaphe's power is equal to your devotion to blue. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)
Creatures and enchantments you control have "Spells your opponents cast that target this permanent cost {1} more to cast."

Negate

High Tide

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

Resculpt

Exile target artifact or creature. Its controller creates a 4/4 blue and red Elemental creature token.

Conjurer's Closet

At the beginning of your end step, you may exile target creature you control, then return that card to the battlefield under your control.

Displace

Exile up to two target creatures you control, then return those cards to the battlefield under their owner's control.

Deadeye Navigator

Soulbond (You may pair this creature with another unpaired creature when either enters. They remain paired for as long as you control both of them.)
As long as Deadeye Navigator is paired with another creature, each of those creatures has "{1}{U}: Exile this creature, then return it to the battlefield under your control."

Reality Shift

Exile target creature. Its controller manifests the top card of their library. (That player puts the top card of their library onto the battlefield face down as a 2/2 creature. If it's a creature card, it can be turned face up any time for its mana cost.)

Ray of Command

Untap target creature an opponent controls and gain control of it until end of turn. That creature gains haste until end of turn. When you lose control of the creature, tap it.

Torrential Gearhulk

Flash
When Torrential Gearhulk enters, you may cast target instant card from your graveyard without paying its mana cost. If that spell would be put into your graveyard, exile it instead.

Watcher for Tomorrow

Hideaway 4 (When this creature enters, look at the top four cards of your library, exile one face down, then put the rest on the bottom in a random order.)
Watcher for Tomorrow enters tapped.
When Watcher for Tomorrow leaves the battlefield, put the exiled card into its owner's hand.

Aether Adept

When Aether Adept enters, return target creature to its owner's hand.

Panharmonicon

If an artifact or creature entering causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.